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I HAVE for a long time entertained the opinion that the accepted 
theory of the relative positions of the feet of horses in rapid motion 
was erroneous. I also believed that the camera could be utilized to 
demonstrate that fact, and by instantaneous pictures show the actual 
position of the limbs at each instant of the stride. Under this con- 
viction I employed Mr. MUYBRIDGE, a very skilful photographer, to 
institute a series of experiments to that end. Beginning with one, 
the number of cameras was afterwards increased to twenty-four, by 
which means as many views were taken of the progressive move- 
ments of the horse. The time occupied in taking each of these 
views is calculated to be not more than the five-thousandth part 
of a second. The method adopted is described in the Appendix 
to this volume. 

When these experiments were made it was not contemplated to 
publish the results; but the facts revealed seemed so important that 
I determined to have a careful analysis made of them. For this 
purpose it was necessary to review the whole subject of the loco- 
motive machinery of the horse. I employed Dr. J. D. B. STILLMAN, 
whom I believed to be capable of the undertaking. The result has 
been that much instructive information on the mechanism of the 
horse has been revealed, which is believed to be new and of suffi- 
cient importance to be preserved and published. 


The HORSE IN MOTION is the title chosen for the book ; for the 
reason that it was the interest felt in the action of that animal that led 
to the experiments, the results of which are here published, though 
the interest wakened led to similar investigations on the paces and 
movements of other animals. It will be seen that the same law 
governs the movements of most other quadrupeds, and it must be 
determined by their anatomical structure. 

The facts demonstrated cannot fail, it would seem, to modify the 
opinions generally entertained by many, and, as they become more 
generally known, to have their influence on art. 








The Horse considered as a Machine. Necessity of understanding its Construc- 
tion. General Physiological and Anatomical Facts. Architectural Prin- 
ciples involved in the Construction of the Skeleton. Of the Joints. The 
Vertebra. The Cartilages and Ligaments. The Muscles, Voluntary and 
Involuntary. General Facts, Anatomical, Physiological, and Mechanical, 
regarding the Muscles. Articular Ligaments. Tendons. The Law of 
Repair in Muscles and Tendons. Relation of the Form of Organs to their 
Functions. Utility made to conform to Beauty in the Form of Organized 
Beings 22 


Special Anatomy. Necessity of Technical Terms. The Ilio spinalis. Defi- 
nition of Terms. Psoas magnus. Iliacus. Tensor Vaginas Femoris. 
Sartorius. Pectineus, Small Adductor, etc. Great Gluteus. Deep Glu- 
teus. Long Vastus. Semi-tendinosus. Semi-membranosus. Great Ad- 
ductor. Gracilis. The Adduction and Abduction of Muscles. Triceps 
Femoris. Gastrocnemii. Automatic Action in the Hind Leg. The Per- 
forans and Perforatus Muscles and their Tendons. Suspensory Ligament. 
Difficulties in the U'ay of determining the Amount of Work done by Muscles. 
Elongation and Contraction of the Limbs. Interference and Stifle Ac- 
tion. The Action of the Hock Joint to prevent Interference. The Order 
of Action in the Various Muscles of the Posterior Extremity in Locomotion . 35 


The Comparison of the Anterior Extremity to the Spokes of a Wheel considered. 
Its Three Characters of Crutch, Passive Tool, and Active Automaton. - 
The Great Serratus. Its Double Character of Tendon and Muscle. 
Centre of Motion. The Trapesius and Yellow Cord. Levator Angu'.i 



Scapulae. Trachelo subscapularis, its Function hitherto unknown. The 
Great Dorsal and Pectoral as Propellers. The Mastoido humeralis as an 
Extensor. The Muscles of the Shoulder-Blade. The Pair of Muscles that 
flex the Shoulder. The Function of the Triceps in resisting the Fall of the 
Body and in Locomotion. Function of the Flexors of the Forearm. High 
Action. Obstacles to a Full Understanding of the Functions of the Loco- 
motive Muscles removed by the Camera. Analysis of the Movements of the 
Anterior Extremity. Mechanical Points desirable in a Horse for Speed or 
Strength. Low Centres of Motion. Long Levers. Comparison between 
the Anterior and Posterior Extremities. Why Quadrupeds rise from Recum- 
bent Positions with Difficulty. Why Boxers and Others liable to be placed 
suddenly on the Defence have their Limbs semi-flexed. Elements of 
Speed 60 


Influence of Gravity constant. Momentum accelerated. The Law of Falling 
Bodies and its Application to Locomotion. The nearer the Trajectory of the 
Centre of Gravity is to a Straight Line the more perfect the Locomotion. 
The Theory of Quadrupedal Locomotion stated. Analysis of the Run. 
The same in all the Domestic Animals. The Bound of the Deer. Why the 
Flexor Tendons of the Fore Legs are more liable to be injured in the Run. 
What is the Gallop? Objections of Artists answered. Truth must prevail 
over Conventionalism. The Canter 83 


The Leap not properly a Pace. Action in the Leap described. The Danger 
to be apprehended in the Leap. The Standing Leap. Correspondence in 
the Action of the Horse in the Leap and the Deer in the Bound. Action in 
the Trot. Distinction between a Step and a Stride. The Difficulty to be 
encountered in increasing the Speed of Trotters. Difference in the Action in 
the Trot and the Run. Difficulty in restraining a Horse from breaking into 
a Run explained. Fast Trotting cultivated in America in Thoroughbreds. 
Trotting not Hereditary, but a Habit. Theory and Mechanical Action in the 
Trot. The Action in Ambling, or " Pacing." Definition of the Walk appli- 
cable to Bipeds, not to Quadrupeds. The Action in the Walk. The Action 
in the Pace known as Single-Foot IO S 






OF THE PACES (Heliotype) Frontispiece 


Colored rafotngs. 































































THE STRIDES (Hdiotype) 124 




THE Horse, of all animals, holds the most important relations to 
the human family. Though the earliest traces of his existence on the 
globe are found as fossils in North America, as an historical char- 
acter he is traced to Central Asia with the Caucasian race. There 
was no representative of the race living in America at the time of 
the discovery of the New World, but it was introduced by Columbus 
and his followers, and its descendants became feral on the Prairies 
of North and the Pampas of South America. They were undoubt- 
edly of Arabian stock, through the Moors ; small, active, and hardy. 
Their descendants were very numerous in what were the northern 
provinces of Mexico, previous to the invasion of Texas. 

The genera were well represented in Africa and the deserts of 
Arabia, but we have no evidence that the historic horse was known 
in Africa before the time of Rameses the Great, in the Eighteenth 
Dynasty, after the wars with the Persians. Nowhere in all the tem- 
ples and tombs of Memphis, Sais, Abydos, of the First Empire, is 
there a sculpture that could lead us to infer that the horse was 
known to the Egyptians of that early age. There are no sculptures 
in India older than the dawn of Buddh, or about five centuries 
before our era. The oldest written account of the horse is found in 
the book of Job, and that is a very spirited description of a war-horse; 
and it is probable that that is the oldest of the sacred writings of 
the Hebrews, though there is no clew to the date or origin of that 
curious production. 


Though the relative importance of the horse as a factor in the 
progress of civilization has been reduced by the introduction of steam 
in our century, it cannot be forgotten that he has been the con- 
stant companion of the Caucasian race in all its migrations, an in- 
dispensable ally in all its conquests, and the most efficient agent of 
its civilization. We have no history that is not interwoven with his; 
and if by some sudden cataclysm he should be eliminated, we should 
then be made to realize how indispensable he still is to our business 
and pleasure. Whatever concerns him will never cease to interest 

The interest in the paces of the horse is not new : it had engaged 
the attention of philosophers from ancient times. Aristotle, the 
father of Philosophy, thought it not unworthy his investigation ; but 
with all other rational questions, it was lost to human thought dur- 
ing the long reign of religious bigotry. When the intellects of men 
were again set free, and Science woke from her slumber, Anatomy 
was studied and taught in the schools, and attention became directed 
to that of our subject ; but even Borelli, who wrote about two hundred 
years ago, and published the work on Animal Mechanics that most 
later writers have drawn upon, thought it necessary that he should 
not confound flesh and muscle. Vital force was as yet unknown, 
and all treated the subject as a physical science, and deduced its 
laws from the motions of the pendulum, and mathematically formu- 
lated them. 

Two brothers, named Weber, who are quoted much by the author of 
"Animal Motion," in the "Encyclopaedia of Anatomy and Physiology," 
followed Borelli on the purely physical theory of Animal Motion. 

Professor Marey has contributed the result of many laborious and 
painstaking experiments on the slow paces, by means of apparatus 
attached to the feet, and connected by elastic tubes with registers in 
the hands of the rider. This apparatus would determine the force 
of the footfalls and time of pressure, and by the system of notation 
a chart could be made of the paces. But it failed to interpret the 
paces correctly, or furnish the basis of a theory of quadrupedal loco- 
motion. The importance of the subject had been fully appreciated by 


him, as appears in the following quotation from his work on Animal 
Mechanics : " There is scarcely any branch of animal mechanics 
which has given rise to more labor and greater controversy than the 
question of the paces of the horse. The subject is of great impor- 
tance to a large number of persons engaged in special pursuits, but 
its extreme complexity has caused interminable discussion. Any one 
who proposed at the present time to write a treatise on the paces of 
the horse would have to discuss many different opinions put forward 
by a great number of authors." 

Bishop, the author of the article on "Animal Motion" in the 
"Encyclopaedia of Anatomy and Physiology," says: "The study of 
the mechanism of which the locomotive organs of animals is com- 
posed, of the laws by which their progression is accomplished, and of 
the vital force which they expend in propelling the body from one 
point in space to another with different velocities, serves to interest 
alike the anatomist and the physiologist, the artist and the mechani- 
cian. Ignorance of these laws has been productive of grotesque 
delineations of the human figure as well as of the lower animals, when 
represented in motion. We have abundant evidence of this in the 
productions of painters and sculptors, both of the ancient and modern 

The difficulty in this, as in many controverted questions, is to 
determine the facts; and the facts have been most difficult to obtain. 
It seems to many unaccountable, that the horse, whose movements 
are so open, should play such a leger-de-pied as to deceive all eyes, 
and give rise to controversies as earnest as did the colors of the cha- 
meleon in the fable. All attempts hitherto made to analyze these 
movements have failed, for it is not possible for the eye to distinguish 
them ; or rather, to state the case more accurately, the mind is unable 
to distinguish the impressions conveyed to it through the eye. 

Controversies were going on to the last as to which foot was ad- 
vanced first in the trot ; whether the toe or heel first touched the 
ground ; whether in a gallop the legs were stretched out fore and aft, 
or the knees were flexed. All were dabbling in the shallow waters 
of a sea whose depths there was no known method of exploring, and 


artists of all degrees fell into the false and conventional manner of 
representing animals in rapid motion, as untrue as were the Greek 
conceptions on the subject thirty centuries ago. To understand how 
little progress has been made in modern times, it is only necessary to 
look at the productions of the best animal painters of our day. 

Why is it that there have been such widely different interpre- 
tations of these movements from the time of Aristotle down to the 
present ? These positions, as well as all others that have been rep- 
resented, are proved by the unerring finger of light to be incorrect ; 
as mechanical anatomy, had it been properly consultec 1 ., would have 
demonstrated to be impossible. 

It is difficult at a glance to conceive how the eye could be so 
deceived ; but a little consideration of the physiology of that organ 
will teach us that no dependence can be placed on it to interpret the 
motion of an object moving irregularly, even at a comparatively slow 
rate of speed. 

It has been shown that the retina of the eye is capable of receiv- 
ing a distinct image of an object in an almost inconceivably short 
space of time, as that of the flash of an electric spark, or a millionth 
part of a second, and that the impression remains for the space of a 
third to a seventh of a second, according to the experiments of D'Arcy 
and Plateau ; and the mind is incapable of distinguishing between 
the first impression and the last made during that space of time, and 
the images run together and are confused. A familiar illustration of 
this phenomenon is furnished by the spokes of a wheel in motion ; yet 
these spokes will appear stationary, if, revolving in the dark, they are 
suddenly illuminated by an electric flash ; or if the end of a stick be 
ignited, and moved rapidly, a continuous line of fire will appear. Here 
there is a continuous line of impressions made upon the retina, and so 
conveyed to the mind. The same is true of the auditory nerve ; when 
vibrations of air are too rapid, they are heard, but not distinguished. 
The reader may ask why it is that the artists of all time, with the full 
accord of all men, and our own eyes confirm the tradition, represent 
the horse in galloping as extending his feet to the utmost, as seen in 
all the pictures of horses racing. My answer is this : We now know 


that it is not true that a horse ever did put himself in the position 
portrayed by the best artists ; and the explanation that I have to offer 
is, that in the gallop the horse always moves his feet alternately, and 
to the same extent; at the limit of extension there is a change of 
direction given to them, nnd their image dwells longer upon the retina, 
and the impressions are more lasting than of the intermediate and 
more rapid movements which the mind is unable to distinguish any 
more than the order in which they are made. 

The ear has been relied upon to determine by the rhythm of the 
footfalls the order in which the feet strike the ground ; and bells have 
been attached to the feet, each giving a different sound. Others have 
studied the footprints, and the feet have been differently shod to dis- 
tinguish the impression made by each foot upon the ground. 

The study of the mechanical anatomy of the horse is a necessity in 
order to a proper understanding of the forces employed and their 
combined action. This necessity has now become more imperative, 
as the action is better understood from the revelations of the camera. 

All the systematic works on the anatomy of the horse have followed 
the plan of those on human anatomy, and apparently for the same pur- 
pose, namely, the intelligent treatment of the diseases and accidents to 
which horses, as well as men, are liable, while the action and relation 
of the machine, as such, have been treated as of secondary importance 
or altogether neglected. It has not been possible to study the action 
of the muscles singly without falling into errors ; the correlation of 
all of them is necessary to the understanding of any one. It is to this 
cause that so many errors and contradictions found in all authorities 
that have been consulted are to be ascribed. Indeed, how was it pos- 
sible that it should have been otherwise, so long as it was not known 
what those actions were ? 

The progressive motions of a quadruped, which must be considered 
as a unit, are very complex ; when so studied it will be found that all 
the parts are mutually dependent, that the forces employed are com- 
pound and often indirect, and that the compensation of one indirect 
action may be found quite remote. When thus considered it will be 
found that the horse in motion is as perfectly harmonious in the dis- 


play of his forces and their balance as a steam hammer, which may be 
adjusted to a force sufficient to forge a shaft for an ocean steamer or 
to crack a nut. 

It cannot be expected that many of those persons who are inter- 
ested in the movements of the horse will be familiar with the anatomi- 
cal terms necessary to be used in the description of the simplest 
motion, and it cannot be made intelligible without them ; much less 
can it be expected that one will be able to comprehend a full stride 
from any analysis that can be given without such knowledge. 

The writer thinks himself warranted in the assertion that the correct 
interpretation of the mechanical action of the horse cannot be obtained 
from any existing work. It is very desirable that it should be under- 
stood by every one who is interested in his achievements, and by artists 
as well. To facilitate this study, technical terms will be emitted as far 
as possible, and where they are employed they will be accompanied by 
popular ones as far as they are known. 

One of the sources of difficulty to the non-professional student is 
the distinctive names given to different tissues whose mechanical 
function is the same. Whether a muscle has its termination in facia 
aponeurosis or at the bone on which it acts, either directly or in- 
directly, may be important to the anatomist or surgeon ; but to those 
who desire to understand the mechanical action it is a matter of indif- 
ference, very perplexing, and a fatal bar to the comprehension of the 
subject ; to such it is of little consequence whether the action is direct 
by muscular attachments to bones, or indirect through facia or other 
fibrous tissue. In all cases I shall use such terms as will most cor- 
rectly give my meaning in the interpretation of their action. 

Another source of confusion in the study of the muscles of mo- 
tion in quadrupeds is the conflicting names given to them. When, 
on the restoration of the cultivation of science, comparative anatomy 
began to attract the attention of naturalists, human anatomy had 
already received much attention, and names had been bestowed upon 
all the principal organs. Some of them were purely fanciful ; others 
were based on their resemblance to other objects. The muscles were 
often named from their supposed function, or their correspondence to 


muscles found in the human body. This last has been the most fruit- 
ful source of confusion, and the mind of the student is constantly 
biassed by this correspondence of names to muscles that do not have 
corresponding functions. It may be taken for granted that organs 
have the same diversity of form in man and animals as there is 
diversity of function, and in each the organisms are just such as best 
serve the offices which they were designed to perform. Some of the 
later authorities have attempted a reform in the nomenclature of the 
muscles, based on their supposed uses, and have only added to the pre- 
vious contusion. Adductors and abductors have been so multiplied 
that it would seem that a horse, like a crab, was made to go sidevvise. 

Anatomy will be treated no further than is necessary to demonstrate 
locomotion ; and those who would pursue it further, and those who 
would be more minute in their knowledge of structure, must dissect 
for themselves. 

The writer has already had occasion to allude to design, and will 
have frequent necessity for doing so in describing the complicated 
mechanism by means of which locomotion in the higher orders of 
animals is effected, and he wishes it understood that he uses that term 
in its literal and highest signification. He does not shrink from the 
use of terms that imply an intelligent Creator and all-pervading Spirit, 
who, from the beginning, established the foundations of the earth, and 
who, in incomprehensible wisdom and power, has fixed the laws which 
govern the organic world from the beginning through all its changes. 

In using the term " higher orders of animals," he follows custom. If 
that distinction is founded on the complexity of his locomotive powers 
or organization, then man could not justly claim the first rank; for if 
his preservation had depended upon his speed in locomotion, he would, 
in the long struggle for life through which he must have passed, have 
taken his place in the earliest paleontological deposits. 

It may seem presumptuous to compare objects, the lowest of which 
are beyond our comprehension. The finite cannot comprehend the 
infinite ; there must be a limit, in the nature of things, to all inquiry 
into the phenomena of life. If physical science could determine the 
laws of that which is hyperphysical, then to its court we might 


carry all cases involving ethical or aesthetical questions, and form 
might be confounded with color. To this pans asinorum all the old 
writers on animal mechanics came. They would test vital force by the 
laws governing the motion of the pendulum or those of gravity. If 
physical science could establish the laws and solve all the questions 
that arise in the investigation of vital phenomena, and algebraic expres- 
sions could represent the unknown quantities, the task would be easy. 
We could calculate the force of the right arm of a warrior as we could 
the weight of his sword ; but when that arm descends, it falls with 
more than the force of gravity. There is a power that must enter into 
all our estimates of vital force, and that is the will. It cannot be 
ignored in any calculation on animal motion ; and yet who can estimate 
it, weigh it, and formulate it, as in the exact sciences ? 

Thomas Starr King used to tell a story of a countryman who 
attracted the attention of a traveller by the fine physical development 
he displayed, and of whom he inquired his weight. " Well, stran- 
ger," said he, " ordinarily I weigh two hundred and thirty pounds, but 
when I am mad I weigh a ton." 

The progress that science has made in every department, and is 
still making, is wonderful, and who can say where it will end ? But in 
the knowledge of the laws which govern the origin of life, the vital 
organs and their functions, of the nature of that force by which one 
form becomes altered or modified by the altered conditions of its life, 
it has made no progress since the days of Job. 

The whole question of life and vital force is still a great mystery, 
although it is receiving at this time the concentrated attention of the 
most intelligent naturalists of all nations. There are not many who 
deny that organic forms may be modified within certain limits by arti- 
ficial means. There are many who believe that all organic beings, of 
whatever nature, had their origin in the most rudimentary element, as 
a cell possessing certain inherent tendencies to develop by aggregation 
into other and higher forms, unequally modified in various ways by 
surrounding influences, with a tendency to variation by imperceptible 
degrees in every direction, the useful variations favoring the existence 
of the individuals possessing them. This idea has become familiar 


under the terms " natural selection" and "survival of the fittest." This 
hypothesis docs not presuppose design, and denies a Creator. Under 
the name of " Darwinism" it has become popular and invaded all ranks. 
It found the soil of Germany especially fitted for the propagation of a 
theory of such an atheistic character, and it was proposed at a meeting 
of the Society of Naturalists at Munich, a few years ago, to teach it in 
the national schools. It has become so generally diffused in our own 
scientific circles that a reference to a Supreme Being in an essay read 
before a society of naturalists would be considered to be a poetic license, 
if one had the courage to make it; and nature is usually personified to 
meet the necessity. We have long been familiar with the reference to 
the laws of nature, and we now begin to hear of the laws of evolution. 
In all ages there has been a tendency on the part of the masses to 
follow some leader whom they desired to do their thinking for them ; 
to pin their faith to his, or what they supposed to be his: it is no less 
so in the scientific circles than in the religious. Dogmatism seems to 
be leaving the latter to attach itself to the former; at all events, it is 
inherent in the human mind; no person is utterly free from it; and to 
appeal to the opinions of those whom we believe to be better informed, 
rather than to examine the foundations of those opinions, has been 
the vice of all ages. 

It is well known that faculties and functions are strengthened 
by use and weakened, or altogether lost, by disuse. We shall look 
in vain for proofs of an organ changed in the mechanical principle 
of its construction, or one evolved by imperceptible degrees where 
none existed before; but we shall, on the other hand, find proofs 
in anatomy that the changes could not have been gradual. Every 
stable-boy knows that qualities are transmitted by heredity, and that 
desirable ones may be bred by judicious crossing within certain lim- 
its; and he knows as much as any one of the force, or influence, by 
means of which this is brought about. Speculation should not be con- 
founded with science, as was said by Virchow, or science will lose its 
claim to the respect of mankind ; and this whole question of evolution 
is speculative when carried beyond proof; and science, when it crosses 
the vital boundary-line, is lost in speculation. We know that organic 


matter is subject to physical laws like other matter: it is attracted 
by the earth, and will fall with a force as great as if it were inanimate, 
and is equally subject to the law of falling bodies; it acquires mo- 
mentum, and its momentum is equal to the weight multiplied by 
the velocity, the same as that of a railway-car, or a cannon-shot ; 
and when vitality leaves it, it is resolved to its original elements, 
oxygen, carbon, etc., which the chemist can prove by analysis. But 
has the most skilful chemist ever been able by synthesis to restore 
the lost element, the vital spark ? Has he ever been able to imitate 
the products of that vital laboratory the stomach, and form the 
aliment that replenishes the blood? 

With all the knowledge of physics ever acquired by man, can he 
make a pump so perfect as the heart, that organ that forces the 
blood loaded with fresh sustenance to every part of the body ? And 
what does he know of that power that has kept it in alternate action 
and rest every instant since before the earliest memories of his child- 
hood ? 

He has been familiar with the laws of optics for centuries, and has 
made instruments of glass and metal, in imperfect imitation of the eye 
of an animal, to exalt the powers of his own vision ; but what would 
not an optician give to be able to construct a concentric achromatic 
lens, with automatic power to adapt itself to the distance of objects, 
such as the eye of the lowest of the vertebrates ? 

Acoustics is another of the physical sciences of which man is a pro- 
fessor, and he has just invented an instrument by means of which he 
can communicate in ordinary vocal sounds to a person miles distant. 
He has recently invented another, by which he can register and pre- 
serve the intonations of his voice to be returned to him at will at any 
future time ; but that most wonderful instrument, the ear, he can only 
wonder at and admire. Without it the world would be without music, 
voice, or sound ; the faculty of speech, our consciousness, memory, 
imagination, affection but it is needless to multiply this class of 
facts. In nothing does man show himself to be the creation of an 
intelligent power more than in his own creative faculty. How great 
have been his achievements in mechanics ! But what comparison does 


the highest bear to the locomotive apparatus or machinery of the horse, 
with its compound system of levers, pulleys, tendons, springs, and mus- 
cular powers, and. that marvellous ingenuity in arrangement to produce 
results which man has not been able to understand until now, and all 
set in motion through telegraphic communication distributed to every 
muscular fibre, and the whole of this complicated system of organs 
co-ordinated and controlled by one central will ? Another incompre- 
hensible mystery of life is, that this complicated machine should pos- 
sess the power, not only to preserve and protect itself through a long 
life, but of reproducing from generation to generation indefinitely, 
and transmitting to posterity its own peculiarities of form and mental 
qualities ! 

Does the whole organic world furnish no proofs of intelligence and 
design, that we must be told that all these marvellous manifestations of 
both are but the inherent properties of matter, 

" And that were true which nature never told "? 

If it were an " attainment and an aim " to escape moral responsibility 
by getting rid of a creator, do we approach any nearer the solution 
of the question of the origin of life by removing it farther off into the 
mytho-geologic eras ? Or is the difficulty in any way diminished by 
attributing to matter all the high intellectual functions that have been 
by unschooled people in all ages ascribed to supernatural powers ? 

Can the microscopist, when he discovers vibriones in a vegetable 
infusion, or protoplasm in a drop of serum, be excusable for running 
naked, like the philosopher of Syracuse, through the streets, shouting 
" Eureka " ? Can one who finds a shingle or a brick claim that he has 
discovered the cause of a house ? Let him account for the origin of the 
brick and the shingle ! 

Because a fossil skeleton of a four-toed horse, which failed to con- 
nect his species with our time, has been found in the fossiliferous 
deposits of the interior of this continent, does it follow that our noble 
soliped had an origin less remote and independent, or that he found 
it necessary and practicable to concentrate his four toes into one, or 
succumb to the altered conditions of his life ? 


All science, in whatever department of knowledge, is retarded much 
by the ignorance and zeal of the multitude who follow on the heels of 
genius. Medicine has its mountebanks, who are dragging a noble 
science into public contempt ; religion has its harlequins, and natural 
science its buffoons, who, as itinerant lecturers, perambulate the towns 
as representatives of learning they do not possess, and put forth as 
proved truth the wildest speculations of enthusiasts, and call them sci- 
ence. It is very common to hear of the origin of man from the ape, 
as if the relation were a scientific truth, when in fact it is only a specu- 
lation ; and all the evidence so far collected from fossil remains as early 
as the tertiary deposits gives no confirmation to the speculation. As 
far away as any trace of the prehistoric man has been found, he was as 
perfectly developed as he is to-day, and as far removed from the ape. 

Darwin is not responsible for what is known as Darwinism. He 
is a model for a naturalist, collecting facts and placing them in their 
relation, drawing his conclusions cautiously, and candidly admitting the 
difficulty when a fact antagonizes the hypothesis he is framing. Not 
so with his zealous disciples, who rush to their desired conclusions 
over his facts, as the fanatical Christians of Alexandria did over the 
last vestal altar of Greek philosophy. 

Organic life is the result either of chance or design ; there can be 
no middle ground.* If the latter, the question of how it was brought 
about will never be solved by man, nor is it important that it should be. 
It is sufficient that a Supreme Intelligent Will is the author and sus- 
tainer of all, a beneficent Spirit, who 

* Virchow, who will be recognized as one of the leaders in the new departure in science and 
the cell theory of development, says : 

" This much is evident. If I do not choose to accept a theory of creation, if I refuse to be- 
lieve that there was a special Creator who took the clod of earth and breathed into it the breath 
of life, if I prefer to make for myself a verse after my own fashion, then I must make it in the 
sense of generalio equiroca (spontaneous generation). Tertiam non datur. No alternative re- 
mains when once we say, ' I do not accept creation, but I will have an explanation.' If that first 
thesis is laid down, you must go on to the second thesis, and say, ' Ergo, I assume the generalio 
equivocal But of this we do not possess any actual proof. No one has ever seen a generatio 
equivoca really effected ; and whoever supposes he has is contradicted by the naturalist, and not 
merely by the theologian." PROF. VIKCHOW, in a lecture delivered before the German Asso- 
ciation of Naturalists and Physicians at Munich, 1877. 


" \V;irms in the sun, refreshes in the breeze, 
Glows in the stars, and blossoms in the trees, 
Lives through all life, extends through all extent, 
Spreads undivided, operates unspent "; 

who has endowed us with faculties to admire the beautiful, the good 
and true, to know why so many things arc as we see them, but none to 
know how* 

\ laving given some of the reasons for his belief in the spiritual ori- 
gin of the organic world, the writer claims his right, whenever he has 
occasion in the following pages to do so, to speak, without danger of 
being misunderstood, of design or contrivance in the same sense that 
he would when referring to similar manifestations of design in a 
humanly constructed machine. 

In a theory of evolution, as the expression of the method in crea- 
tion, the writer has little doubt that the thoughtful mind will in 
due time rest satisfied. 

* " The consciousness of an inscrutable power, manifested to us through all phenomena, has 
ln.i n growing ever clearer, and must be eventually freed from its imperfections. The certainty 
that, on the one hand, such a power exists, while on the other-hand its nature transcends intui- 
tion, and is beyond imagination, is the certainty towards which intelligence has from the first 
been progressing." HERBERT SPENCER, First Principles, 3d edition, p. 108. 

' When the remarkable way in which structure and functions simultaneously change is borne 
in mind, when those numerous instances in which nature has supplied similar wants by similar 
means are remembered, when, also, all the wonderful contrivances of orchids, of mimicry, and 
the strange complexity of certain instinctive actions, are considered, then the conviction forces 
itself on many minds that the organic world is the expression of an intelligence of some kind. 
. . . Organic nature then speaks clearly to many minds of the action of an intelligence resulting, 
on the whole and in the main, in order, harmony, and beauty, yet of an intelligence the ways of 
which are not as our ways." ST. G. MIVART, F. R. S., in Genesis of Species, pp. 272, 273. 

"There is something in organic progress which mere natural selection among spontaneous 
variations will not account for; this something is that organizing intelligence which guides the 
action of the inorganic forces, and forms structures which neither natural selection nor any 
other unintelligent agency could form." MURPHY, Habit and Intelligence, Vol. I. p. 348. 





IT is proposed to present as concise a view of the locomotive 
organs of the horse as may be consistent with a proper knowledge of 
the parts, and the functions they perform in progressive motion. 

There can be no just appreciation of the qualities of a complicated 
machine without a comprehensive understanding of its construction, 
and the manner in which each of its parts acts to produce the com- 
pound movement for which it was designed. So, in order to under- 
stand the paces of the horse, we must understand the action of all 
the parts of the machinery by which they are produced. It need 
not be said that it is very complex, and has never been understood, 
for the reason that the motions themselves have been altogether mis- 

This study of the mechanism of the horse is a necessity which will 
become apparent to any one who undertakes to analyze these move- 
ments by the aid of any manual of anatomy yet published. The dis- 
tinction of muscles into adductors, abductors, extensors, and flexors 
gives a very inadequate idea, and sometimes a very erroneous one, of 
the action of the muscles to which those terms are applied, as well as 
to their general agency in locomotion. In fact, these terms are used 
to express the action abstractly with reference to the bones to which 


they are attached, and not sufficient attention has been given to their 
action in correlation to the others with which they are coworkers. 
The forces employed in each limb, considered alone, are very complex. 
The same muscle may be an extensor at one time and a flexor at an- 
other in the same stride, as we shall show further on. 

In order to enable the reader to understand the muscles and their 
relations without too great a tax on the powers of abstraction, the ser- 
vices of Mr. William Hahn.a Diisseldorf artist, were secured to delineate 
the most important muscles as they were exposed in dissection ; but no 
skill can do justice to the nacreous tints of the tendinous envelopes 
of the deep muscles. With all the aid which art can render, the 
complicated mechanism of the horse cannot be presented by written 
description in such a manner as to dispense with a little close attention. 
A perfect familiarity with the subject, so as to enable one to carry 
the plan of the whole machine in the mind, can only be attained by the 
aid of dissection. A knowledge of the construction of the machine 
is imperative upon one who would comprehend its action. It is 
as necessary as for an engineer to understand the construction of his 
engine. With that knowledge one can understand the elements of a 
horse's strength and speed, analyze his movements, and appreciate the 
source of the danger from injury in great trials of speed. 

Let us first review certain physiological and general anatomical 
facts, well, but not so generally known, as could be wished. The me- 
chanical parts divide themselves into two classes, the active and pas- 
sive. The passive parts are the bones and ligaments ; the active parts 
are the muscles in which dwells all the power. 

Of the bones it may be said, in general, that they are the levers on 
which the muscles act, and by means of which their power is made 
available ; their form depends upon the uses which they are designed 
to serve. When intended for bases of action, they are thin, angular, 
and ribbed, like the shoulder-blade, or scapula. When they are to serve 
as columns of support, they are cylindrical ; and as there is always 
the utmost economy used by the Creator where it is needed, they are 
made hollow, for it was known, as long ago as the first mammal was 
made, that there was no loss of strength as a support in being so con- 


structed. It was long afterwards discovered by man, and the law was 
learned by him, that the lateral strengths of two cylindrical bones of 
equal weight and length, one being solid and the other hollow, are to 
each other as their diameters ; and the spaces in the shafts of these 
bones, being needless for the purpose of support, are made depositories 
of fat or marrow for fuel, literally, coal-bunkers, as are all the angu- 
lar spaces not needed for more important uses throughout the body, 
by means of which heat is developed, which primarily is the source of 
all motion in the animate as well as the inanimate world. 

The extremities of these bony columns are spread out to give 
broader articulating surfaces ; at the same time the single hollow of 
the shaft is divided into innumerable small ones, so that greater 
strength is attained to resist the wrenching force to which they are 
liable, without increase of weight ; roughened ridges, spines, and pro- 
tuberances * are formed to give greater surface for the attachment of 
muscles. For the purpose of still further increasing the surface for 
attachment of muscles, supplemental bones are added, as in the splint 
bones, or, as they are called by anatomists, the little metacarpels, 
which not only serve to widen the articulating surface, but, by a strong 
ligamentous membrane that connects them with the main pillar, give 
the necessary space for attachment of important muscles, and where 
the distance from the centre of motion renders the reduction of weight 
very important, as the rapidity with which these extremities move 
increases greatly with the distance from the centre of motion. The 
bones are composed of animal and earthy matter, in the proportion 
of about one of the former to two of the latter. If the proportion 
of the former is increased, they will bend under the force applied to 

* Atheists maintain that function makes the organ ; but how can we conceive of function 
without previous conception of the organ ? What conception can be formed of sight without 
the existence of the eye ? It is held by them that the roughened ridges and protuberances of 
bone are developed by traction of muscles upon the bony surfaces. If this is so, why is it that 
the surface of the bone above the acetabulum which receives the insertion of the recttts fctno- 
ris is smooth ? It certainly is not because there is want of traction on the part of that muscle. 
On the other hand, the tensor vaince femoris and the superficial glutens, whose insertions are 
low down on the femur for the necessary leverage, must find room between other muscles, and 
a rough protuberance is formed to give the most surface for attachment in the least space. 


them ; and if the proportion of the latter is increased, they are liable to 
break. Variation from the normal proportions is the result of disease, 
and is more common in the human family than among quadrupeds. 

The bones are covered with a compact, inelastic fibrous membrane, 
the periosteum, which adheres so closely to their surfaces that consider- 
able force is required to detach it. This membrane serves not only to 
nourish the bones through its blood-vessels, or vascular system, but to 
strengthen them and increase their elasticity. The Californian Indian 
adopts the same method, for the same purpose, in the construction of 
his bow. In studying the architecture of the skeleton, as a whole, it 
will be found that no element of strength is wanting, or principle of 
mechanics violated, in its structure. The bones are arched or bent 
when such forms give greater strength. They are connected to each 
other by a strong tissue, so flexible as to allow of the greatest free- 
dom of motion, but inextensible, and, under all ordinary use, too strong 
to be broken or detached from the bony levers whose motion it is 
designed to limit. It is, however, sometimes torn, either completely 
or partially, in dislocations or sprains ; and the slightest injury to this 
tissue is a serious accident to an animal whose value depends on the 
soundness of his locomotive organs. 

The extremities of bones which move upon each other, as at the 
joints or articular surfaces, are covered with a peculiar formation 
known as cartilage. It is insensible in a state of health, and very 
elastic to pressure ; thickest where most exposed to concussion, and 
covered with a membrane which secretes a glairy fluid adapted to 
lubricate the opposing surfaces and reduce friction. These joints are 
all closed to the admission of atmospheric air and all foreign sub- 
stances, for their admission would soon cause serious injury. 

The joints are divided by anatomists into several classes, according 
to their mechanical construction. Some are simple hinges, admit- 
ting of motion in one direction only, as those of the lower parts of 
the extremities. The heads of all the four columns of support are 
provided with a kind of joint known to mechanics as the ball and 
socket. This form admits of the greatest freedom of motion in every 
direction ; but the motion is limited in extent by capsular ligaments 


which surround the joints as a continuous collar, whose borders are 
attached to each of the bones so far from the opposing surfaces as not 
to intervene, and yet not so far that they may not limit the motion to 
its needs. These capsular ligaments serve another useful purpose. 
Being air-tight, when the limb is off the ground it is supported in its 
place by the pressure of the atmosphere, estimated by Borelli to be 
equal, in the hip joint of a man, to a lifting force of twenty-six pounds. 
The force thus gained is set free to be employed in locomotion. Each 
joint constitutes by itself an interesting subject for study, as they all 
differ in some important particular, according to their uses. The 
construction of the hock joint is quite unique, and has no analogue 
in man ; and that of the hock of the ox is quite different from that of 
the horse. The interlocking grooves are oblique, so that when the 
posterior extremity is brought forward to pass its fellow, fixed upon 
the ground, it is carried obliquely outward, independently of volition ; 
and when all danger of interference is passed, and the limb is again 
extended to reach the ground, the foot is carried obliquely inwards, to 
resume its place under the centre of gravity. This will be referred to 
more fully when considering the action of the posterior extremity. 
The construction of the joints at large would serve as a subject for a 
monograph of great interest; but to be fully understood it must be 
studied ensis in manu. 

A detailed description of the bones will not be attempted. They 
are proverbially a dry subject ; but for the convenience of those 
who require it, a reference plate is presented, lithographed from a 
photograph; and it is hoped that it will, through the eye, give the 
necessary information to enable the reader to understand the mechan- 
ical movements without the study which abstract description would 
require. But the vertebra, or spinal column, as the keel or bed-plate 
connecting the various parts of the machinery, requires further 

The term "spinal column," as applied to the skeleton of quadrupeds, 
is a misnomer, derived, like most anatomical names in comparative 
anatomy, from its analogue in man. The spine being horizontal 
in quadrupeds, and not vertical, as in man, the term " column " 


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is inapplicable to them. The word " spine " is also objectionable, 
as it is derived from the processes which superficially mark its 
course. There seems to be no objection to the term " vertebra," as 
a collective noun applied to the whole or any number of its parts. As 
it is the keel and connection of the various parts of the animated 
engine, so it is the term from which has been derived the name for the 
whole divi>ion of animals to which quadrupeds belong, Vertebrates. 

The vertebra of the horse is divided into five groups, differing ma- 
terially in their mechanical, even more than in their physiological rela- 
tions. These groups are the Cervical, the Dorsal, the Lumbar, the 
Sacral, and, lastly, the Caudal. The cervical vertebras have an im- 
portant relation to locomotion, second to no other division. They are 
provided with spines along the median plane, as are all the vertebrae, 
and transverse projections or processes, which afford attachments to 
ligaments to maintain their relative positions ; and with important 
muscles, as will be shown in a subsequent chapter. There is great 
freedom of motion of these bones upon each other, in comparison 
with those of the next two divisions, especially at the articulation with 
the head and the first vertebra of the trunk. This last is a ball and 
socket joint of a peculiar construction, to enable the animal to reach 
the ground, as in grazing and drinking. 

The second group is the dorsal, and it consists of those vertebras 
that are articulated with the ribs. Like the cervical, these are pro- 
vided with transverse processes, which serve not only for muscular 
and ligamentous attachments, but as braces to the ribs. The spinous 
processes are longer than those of any of the other vertebras, especially 
along the withers, where the suspending muscles of the anterior extrem- 
ity originate. It will be apparent to the most superficial observer that 
the motion, either lateral or vertical, of the dorsal vertebrae upon each 
other is very circumscribed, being limited in a vertical direction by the 
long spinous processes and their intermediate inelastic ligaments, and 
in a lateral direction by the transverse processes and their articulating 
ribs. The next division is that of the lumbar region, or the vertebras 
of the loin, with which there are no connecting ribs. As the former 
group was more intimately related to the thorax, so those of the lum- 


bar are in the same relation with the abdomen. Their broad and 
long transverse processes afford a protecting roof to the abdominal 
viscera, and give attachment to important muscles of locomotion on 
the under surface. There is very little movement of these bones 
upon each other, even less than in the dorsal series, so little that 
bony union takes place between them in old age ; and the elastic 
cartilages that, at an earlier period of life, were interposed between 
each of the vertebra become degenerated into bony matter, and that 
condition obtains technically known as ankylosis. 

The next series, and fourth in order, is the Sacral. Though in 
the embryotic stage the sacrum is developed from several centres as dis- 
tinct vertebra, yet before birth they are united into one broad triangular 
bone, which, uniting with the iliac bones on each side, and the pubic 
bones in front, forms the ring known as the pelvis. It is in the lower 
or pubic portion of this pelvis that the cuplike cavities are formed 
into which the heads of the hip bones are lodged, and where the force 
of the levers of the posterior extremities is applied. The difficulty 
in locomotion that would be experienced from the want of flexibility 
of the spine, especially in old age, is obviated by the freedom of 
motion that is secured in the articulation of the last of the dorsal 
vertebra with the sacrum. This is what is known as the "coupling," 
as it unites the two distinct systems of locomotive organs, the anterior 
and posterior extremities. In the skeleton the connection seems very 
slight; but the ligamentous connections are very strong, and the long 
muscle of the back (longissimus dorsi or ilio spinalis), reaching out 
from its spinal attachments, lays hold of the hip bone (crest of the 
ilium) on each side as far as possible from the centre of motion at the 
coupling, the more effectually to limit the flexion at that point. 

The last group of vertebral bones is known to anatomists as the 
coccyx, from its resemblance in man to the beak of the cuckoo; but as 
the resemblance totally fails in the Mammalia and all other vertebrates, 
we shall call them by the more general name of Caudal bones. They 
have no function in locomotion ; but " thereby hangeth a tale." 

Between all the vertebral bones is interposed a layer of clastic carti- 
lage, of the same nature as that which covers the opposing surfaces 


of the joints in the extremities. These cartilages by their elasticity 
admit of slight flexion of the vertebra, and they also deaden the force 
of the shock transmitted from the powerful impulses of the posterior 
limbs. As has been already stated, the flexion is limited by the liga- 
ments which bind them to each other. This restriction of motion is 
necessary for the protection of the vital organs of the thorax and 
abdomen, as well as the great nerve trunk transmitted through a 
continuous canal above the bodies of the vertebra, and which is dis- 
tributed thence to all parts of the body. 

While the three central divisions of the vertebra may be curved 
slightly, they cannot be shortened, even temporarily, as may be readily 

:i ; and the apparent shortening that takes place when the animal's 
limbs are gathered under him is an illusion. The elasticity of the 
cartilages and ligaments is greatest in the young ; as age advances, 
these tissues become stronger and less flexible, and resist the move- 
ments of the joints; they are said to become "stiff." Hence the 
importance of early training to give greater sweep and freedom of 
motion. This physiological principle is made the basis of gymnastic 
training by acrobats, being commenced at a very early age; and the 
same is not lost sight of in the exercises of colts. 

In contemplating the passive parts of the animated machine ab- 
stractly, we see the results of organic life ; they are without sensi- 
bility or power of spontaneous motion ; we are familiar with the 
mechanical principles involved in their action, and are impressed by 
the perfect adaptation of means to ends ; we look upon them as we 
look upon the piston, connecting-rod, and crank of a steam-engine : 
but upon the muscles we look with far different thoughts ; their action 
has no similitude in the inanimate world. 

The general appearance of muscle is too familiar to every one to 
need description ; its special vital property is contractility. The mus- 
cles are both voluntary and involuntary, but it is only the former that 
are concerned in locomotion. 

If we remove a fragment of muscle from an animal recently killed 
and examine it closely, we shall find it to be made up of longitudinal 
fibres of a red color bound together by gray fibres of a different tissue. 


If we lay this flake of muscle upon a plate and scrape it gently in the 
direction of its fibres with a dull knife, we shall find upon the edge of 
the knife a red pulp without apparent fibre or tenacity, and there will 
be left behind a bundle of strong cellular tissue. It is to the former 
that the tractile property belongs ; the latter has no more active power 
than other cellular tissue ; yet this pulpy bundle of fibres, as muscle, 
contracts under the stimulus of the will with almost inconceivable 
power. Borelli estimated that the force exerted by the deltoid muscle 
of man in supporting a weight held horizontally in the hand was two 
hundred and nine times greater than the weight. Therefore a weight 
of sixty pounds held horizontally requires an expenditure of contractile 
force of the extensor muscles at the shoulder of more than six tons. 
He demonstrated that the force of the extensors employed by a porter 
in carrying a weight of one hundred and fifty pounds upon the shoul- 
der exceeds three tons.* It follows that this enormous power is 
exerted on the extensors of each leg alternately. 

The natural stimulant to the muscle is the will transmitted through 
the nerves; but the will is not necessary to muscular contraction, as it 
has no influence on the muscles of animal life or the vegetative func- 
tions of animals, and any of the voluntary muscles may be cut off from 
communication with the brain by severing its nervous connection ; yet 
contraction may be excited in the muscle so cut off, and this may be 
continued indefinitely by further division to a microscopic degree ; still 
the fibres will be observed to contract upon the slightest touch, so 
closely are the nervous fibres interwoven with those of the muscle. 

Electricity when passed through the muscle in a broken current is 
a strong excitant to muscular contraction, overmastering the will, and 
will even cause contraction after life has left it ; but if the current is 
continuous, it has no such power. 

The muscular fibres are paralyzed by certain poisons, and stimulated 
to violent contraction by others ; and in disease, as tetanus, they may 
be so violently stimulated as to be torn asunder. This subject, though 
very interesting, is leading away from the special inquiry to which we 

* Cyclopaedia of Anatomy and Physiology, art. " Animal Motion." 


are limited. The muscles are subject to fatigue, and are unable to 
respond indefinitely with equal force to the will. 

Muscular fibre has other properties to be considered in relation to 
motion. Its contractility is limited to one fourth* or one third t of the 
length of the fibre, and with a power proportioned to the area of the 
transverse section of the muscle. It will be found that the relation of 
length to thickness is as action to power. 

Deep-seated muscles are often attached to the bones upon which 
they act directly ; but as there is insufficient space on the surface of the 
bones for all that depend upon them, the extremities of the muscles are 
often changed into tendon, a substance altogether different in its me- 
chanical properties, being compact, very flexible, and incapable of elon- 
gation, in order that it may not give away the contraction effected by 
the muscular tissue. By means of this tendinous tissue the power of 
the muscle is transmitted when necessary to a considerable distance, or 
its direction may be changed by the tendon passing through a sheath 
or groove, as a pulley, over an angle. In a humanly contrived machine 
it has been found necessary, when the direction of the action of the 
power requires to be changed, to use a friction roller or pulley ; but 
nature has done better, and contrived a way to avoid friction and wear 
that human ingenuity cannot hope to rival. By these means the power 
generated in the heavy muscles is exerted at the extremities of the 
limbs where all needless weight requires such great expenditure of 
power to give it the needful velocity. The power which is conserved 
in the body as momentum would be lost in the extremities, for the 
motion of the limbs is arrested at every stride. $ The attachment 
of these tendons to the bones and the periosteum enveloping them is 
so great that detachment by natural means is not mentioned in 
works on farriery as among the possible accidents to which the horse 
is liable. 

* Bishop. 

t Bowman, Cyc. Anat. and Phys. 

J If a weight of 25 Ibs., sustained by the hand of an arm extended horizontally, requires the 
expenditure of an energy equal to 2oq times that weight, or 5,225 Ibs., what amount of muscular 
force is expended by the muscles of one of the extremities of a horse to move a 4-ounce shoe on 
his foot when he is trotting at the rate of a mile in 2 min. 20 sec.? 


During the life of the animal the tenacity of the muscle is greater 
than that of its tendon, but when vitality no longer animates it it may 
be easily torn. 

While the articular ligaments are subject to extension and elonga- 
tion by early use and frequent tension, so that greater freedom of 
motion than, is normal is acquired, it is otherwise with the muscular 
tissue and its tendons. By exercise within certain limits, at regular 
intervals, and with proper nutrition, the thickness and power of the 
muscles may be increased, and by neglect of these conditions they will 
become thin and pale, while contraction will be feeble and not well 
sustained ; but they will not become elongated under whatever violent 
and long-sustained exercise ; they may increase in thickness, but not 
in length. But for this exception to the rule the whole plan on which 
animal mechanics was founded would have fallen to the ground with 
the animal himself. Were the muscles to become lengthened by use 
without corresponding increase in length of levers, the tension neces- 
sary to prompt action would be lost, and the effect would be similar 
to that upon the tiller ropes of a ship were they to become relaxed. 
What would be the effect upon the length of the bones in the period 
of time contemplated by some it is useless to inquire, but we know 
that the increase of muscular power by increase in the bulk of the 
muscle takes place in a short period, and in the lifetime of the indi- 
vidual. But while the muscles and their levers will retain their nor- 
mal relation of length during life in a healthy subject, that balance is 
sometimes lost as the result of injury. A child has been run over by 
a wagon ; the wheel has passed over the muscles of the calf so as to 
disorganize the muscular tissue; in due time the injured part is re- 
stored to health, but the muscle does not develop fully ; it is shortened, 
and a form of club foot is the result, in which the person cannot, while 
walking, reach the ground with the heel. The child has grown to 
manhood, but no amount of use and no length of time will elongate 
the muscle. Nature cannot elongate that muscle without anarchy. 
The Creator works by law, and to claim an exception is virtually an 
admission that we do not understand the law. But what He cannot 
do without anarchy his creature can ; he slips a tenotomy knife 


beneath the tendon, severs it with scarcely a visible external wound, 
the muscular fibres retract the severed ends, and that ever-present, 
inscrutable power fills in the space left by the parted extremities of the 
tendon with new tendon, the organ is restored to proper length, and 
the deformity is removed. If, on the other hand, one of the bony col- 
umns of support be broken, for example, the thigh, the creative 
power called nature soon sets at work to repair the damage. A seques- 
trum, or casing, is formed around the broken extremities, consisting of 
inelastic bony matter, to fix them in their position as a temporary expe- 
dient, while the slower processes of the more thorough organization of 
perfect bone is effected, and the fracture is repaired, after which the 
sequestrum is absorbed and carried off through the circulation. While 
this change has been taking place in the bone, it would, without surgi- 
cal interference, in most cases be shortened by overlapping through the 
contraction of the muscles on all sides of it. The consequence would 
be that the same disaster would be encountered as in the last case, 
where the muscles were supposed to be elongated from use ; but another 
law is observed. The muscle that could not elongate will shorten, and 
the proportion between the length of the lever and the muscles which 
act upon it is restored. 

It is said by Professor Marey that " the comparison between ordinary 
machines and animated motive powers will not have been made in vain 
if it has shown that strict relations exist between the form of the organs 
and the character of their functions ; that this correspondence is regu- 
lated by the ordinary laws of mechanics ; so that when we see the mus- 
cular and bony structure of an animal we may deduce from their form 
all the characters and functions they possess." This statement, which 
/;/ the main appears to be true, requires qualification. The form of 
many muscles is made to conform to the situation and relation of sur- 
rounding organs. Nature, while prodigal where she can afford to be, 
i.^ economical where there is need of it. This is shown in numerous 
ways, and especially in the form and arrangement of muscles. 

Beauty of form is never lost sight of in the construction of the 
horse; and even great sacrifices of mechanical power are made to 
maintain graceful lines, and that general contour of form that gave 



to him his matchless beauty, beauty so great that to the eye of a 
superficial observer it is difficult to decide whether it is subordinate to 
strength or conversely. Both are developed in a perfect horse to such 
a degree that he has been a favorite theme of poets and painters since 
aesthetic culture has had a place in the history of our race. 

Numerous instances might be referred to where use has been sacri- 
ficed to economy of space and to beauty; but they cannot fail to occur 
to the mind of the anatomist ; and it is premature to introduce them in 
this place for the general reader. 





FROM the general observations of the last chapter we will proceed 
to a consideration of the special anatomy, and analyze the locomo- 
tive organs of the horse ; without this preparatory study it will be 
impossible for any one to analyze its movements. 

Those who have studied and suppose they understand this action 
must study again. Let no one be turned from this subject by tech- 
nical terms ; they are indispensable in order to make one's self under- 
stood by those who have already made a study of anatomy, as well 
as to those who would follow the movements by which the various 
paces are performed, and speak of a horse in more intelligible terms 
than the slang of jockeys and the stables. I think I am warranted 
in the belief that we are on a new era in the history of our old 
friend and fellow-traveller; the increasing interest that is felt in 
America as well as Europe, and the impulse that is sure to be com- 
municated by the wonderful revelations of the camera, justify me 
in that opinion. I shall not follow the usual order of descriptive 

It has already been stated that it is not the purpose of this essay 
to teach anatomy any further than is necessary to demonstrate the 


mechanism of the locomotive organs, and the manner in which the 
muscles act upon their bony levers to produce the movements in 
progressive motion. 

The long muscle of the back holds the same relation to the loco- 
motive muscles that the vertebra does to the bones ; it is a very com- 
plex muscle or system of muscles ; it is called by Chauveau the ilio 
spinalis, so named from its attachments. It fills the angular space 
on each side of the spinous processes, giving roundness to the back. 
It is very broad and thick over the loins, and is attached to the 
whole anterior border of the ilium and strongly to its crest, or the 
hip bone, as seen in Plate III., q; it is attached anteriorly to all 
the spines of the vertebra, as far as the neck, and a strong mem- 
brane, tendon-like in its construction, that is firmly fastened to the 
same bones. This tendinous membrane, called aponeurosis, has 
not been mentioned thus far, but it is tissue very important in 
its relation to the muscles; it differs from fascia in several respects, 
but specially in thickness and strength. It covers nearly all the 
superficial muscles, and its strength is so great that the muscular 
fibres are attached to its inner face as to a bone, and it serves them 
often the same purpose as fixed attachments.* 

If one takes an elevated seat with the driver on a coach, and 
looks down upon the wheel horse nearest him, he can see the action 
of this muscle, and to the best advantage if the horse is trotting. 
It will be noticed that the spine is flexed in a serpentine manner 
as the diagonal legs move alternately. This movement is caused 
by the impulses given to the pelvis by the heads of the femurs 
alternately, which would seriously strain the articulation of the pel- 
vis with the lumbar vertebra called the coupling, but for the action 
of the ilio spinalis, which contracts simultaneously with the impulse 
communicated to the opposite side of the pelvis, acting as a brace 
checking the wrenching violence of the action and preventing 
injury to the coupling. This is the function of the iliac wings, as 

* A familiar example may be seen in a porter-house steak of beef. The part known as 
the tenderloin is a section of the psoas ; that above is a section of the ilio spinalis over- 
laid by its aponeurosis. 



referred to in Plate V., a, a, a. The great mass of the muscle 
which fills the angular spaces on each side the spines is called 
into action in rearing, or supporting, the anterior half of the body 
when not supported by one of the fore legs. The greater part 
of the ilio spinalis is concealed in the plate by the great glu- 
tcus, f, f, c. The centres of motion between the vertebra are in the 
bodies of those bones which are most distant from the spines, and 
which form the rounded ridge of the backbone as seen in the great 
cavity of the trunk. In man they constitute the supporting column. 
The ilio spinalis muscle lies wholly above this axis, and its action 
abstractly would curve it downward ; it can have no influence, there- 
fore, in aiding to support a back load. The mechanical action of 
this long and powerful muscle is therefore, first, when they both act 
in unison to support the anterior half of the body while the pelvis 
is fixed by other muscles; and in the second place, when they act 
alternately, to counteract the wrenching effect of the propulsion of 
the heads of the thigh bones. 

Before we proceed any further with the consideration of the mus- 
cles of locomotion, we must agree upon the signification of terms 
necessary to be employed. 

The words " flexor " and " extensor " may be proper enough in some 
of their applications and express fully the action, but not in all. Some 
muscles act as flexors and extensors at the same time ; others are exten- 
sors at one part of the stride and flexors at another ; and some of the 
most powerful propellers in the whole machine are flexors, as we shall 
show in the course of this treatise. It will be seen that the actions 
of the muscular powers are sometimes quite too complicated to be 
expressed in one word. 

The term " extensor " is commonly applied to all muscles whose 
action is to enlarge the angles and by so doing elongate the limbs ; 
but this extension may be forward when the foot is in the air, or back- 
ward when the foot is on the ground. There is no word in use by 
anatomists to express the fundamental idea, propulsion. The terms 
" flexion " and " extension " will be used in the following pages to 
express the action of a muscle upon its attachments, without reference 


to its functions in locomotion. The words " adductor " and " abduc- 
tor," meaning the function of drawing to or away from the vertical 
plane passing through the axis of the body, are well enough, but we 
must not be misled by the application of these names to muscles which 
may have such action to the extent only of five per cent of their work, 
and the rest, or eighty-five per cent, devoted to propulsion. 

I have already referred to the misnomers in muscles ; they mislead 
the mind no less with regard to their action than to their form and 
construction. 'What can be more inappropriate than the names semi- 
membranosus and semi-tendinosus, meaning half membrane and half 
tendon, when applied to the muscles so named in the horse ? They 
are well enough when applied to the corresponding muscles in man, 
but in the horse they are not at all membranous or tendinous. 

We should be glad to dispense with names altogether, and apply 
abstract or algebraic terms to avoid misconceptions, if practicable, but 
we must use such as are given, and, where there are synonymes, use 
such as are least liable to the objection referred to. 

There is a group of muscles whose action is to advance the whole 
posterior extremity after the act of propulsion is complete. They are 
all deep-seated, with two exceptions. 

1\\Qpsoas magnus (Plates VI., VII., a, a) has its origin in the abdo- 
men, along the under surface of the lumbar vertebra ; its fibres, which 
determine the course of its action, are directed backward and down- 
ward, and it terminates in a long tendon which is inserted into a rough 
ridge on the inner side of the femur, or thigh bone, just below the head 
of the bone ; another of this group is the iliacus (c, Plate VII.), which 
arises from the lower face of the ilium, or hip. The course of its fibres 
is similar to that of those of the psoas, but its origin being farther from 
the median plane, its direction is more inward to join the last-named 
muscle at the same point on the inner face of the femur. These two 
muscles are of delicate organization, and, though differing in form, unite 
in their function of flexing the femur upon the pelvis, and so carrying 
the whole leg forward. The iliacus, having its course more inward 
than the 'other, has the effect of carrying the free end of the femur out- 
ward, the " stifle action," so important in the trotting horse. 



' '. t 



The ten nor vagimc femoris (Plate III., a, a) has its fibres spread 
out beneath the skin and the broad fascia of the thigh. It has its fixed 
insertion in the crest of the ilium, or hip; its fibres arc about eight 
inches in length, and its weight not less than two pounds; its action, 
direct and indirect, is upon the thigh to flex that bone upon the 
pelvis ; from the shortness of its fibres its action as a flexor cannot 
extend beyond three inches, but, being exerted at the commencement 
of the flexion, when its aid is most required, it is very useful. It 
is intimately associated locally and functionally with the superficial 
glutens, which lias one of its attachments at the hip bone, and an- 
other at the thigh bone, or femur, about one third of the distance 
from its head. This portion, therefore, acts with the last mentioned 
in flexing the thigh; the other branch extends alongside of the long 
vastus, filling the angular space made by that muscle where it crosses 
the great glutens. (This is made clear by Plate IV., where the muscle 
under consideration is dissected away, along with the tensor vaginae 
femoris.) It will be seen that it arises from the spine, in front of the 
origin of the long vastus, v, v, v, and its tendinous insertion is at 6, 
or third trochanter of the femur (see skeleton, Plate II., 6); the action 
of this division is therefore that of an extensor, and directly over the 
head of the femur at e, as we shall see when we come to consider the action 
of the posterior extremity as a unit in locomotion. The action of this 
muscle has been a controverted question. Blain teaches that it is a 
flexor of the thigh, Bourgelot classes it with the extensors, and Chauveau 
is of the opinion that it is an adductor. This confusion has evidently 
arisen from confounding the action of its two branches. From these 
two fixed insertions, so remote from each other, the fibres converge to 
the movable insertion at the ridge on the femur, as already stated, 
about one third down the length of the shaft, and between them the 
fibres of the muscle are lost in the fibres of the underlying muscle and 
barely distinguishable in the plate. The form of this muscle has never 
indicated its use in locomotion, but when removed, as in Plate IV., its 
value as an element of beauty is made apparent. 

The sartorius (Plate VI., i>) of the old authors, so called from its 
analogue in man, and so called in man because it is the muscle which 


enables him to assume the cross-legged position of a tailor, is named 
by Chauveau the long adductor. It has its origin on the tendons of 
the psoas muscles at a distance from the mesian plane equal, in the 
normal position of the animal, to that of its insertion at the inner head 
of the tibia. The distance of its corresponding origin in man would 
carry it fully seven inches farther outward and across the great body of 
the iliacus muscle. Its action, therefore, is simply as a flexor of the 
thigh upon the pelvis, but from its great length, eighteen inches, it has 
a sustained action in carrying the limb forward to a new position.* 

There are some' other small muscles, such as the pectincus, small 
adductor, etc., whose weight is so inconsiderable, and whose action is so 
near the centre of motion, that they cannot be supposed to have any 
special influence in locomotion. They are of more interest to com- 
parative anatomists, but mechanically they are of small weight. The 
action, such as it is, seems to be allied to the last, or that of adduction, 
to preserve the balance between the adduction and abduction of the 
great propelling muscles, for it appears to be true that nothing in the 
animal economy was made in vain, and no vacuum exists. When 
the ancients propounded the law that "Nature abhors a vacuum," they 
" builded better than they knew." 

In the complicated mass of muscular forces involved in each of the 
propelling limbs of the horse, it is impossible to determine whether 
adduction or abduction predominates: under the exercise of the will, 
either may do so ; but when the mind of the quadruped is directed to 
some exterior object, to the attainment of which the co-ordination of 
all the locomotive forces are necessary, the adductor and abductor 
action of the muscles may be considered literally side issues, and the 

* Herein lies a curious conundrum for the Darwinians of the atheistic school. If changes 
were by insensible degrees, how did the origin of this muscle become transported from the 
superior spinous process of the ilium in man, to the tendons of the psoas muscles across that 
body of the defenceless iliacus ? That it should have been effected by imperceptible degrees 
seems entirely out of the question ; and as there is a doubt as to priority in order of descent, 
or ascent as the case may be, we will take the liberal side, and admit that the two families, 
Equus and Homo, are of equal age and still evolving, but like parallel lines they can never meet ; 
that the Equus can never be so much as a ninth part of a Homo, or a Homo so much as an 
Equus asinus without tangling his legs worse than with a too free use of his favorite beverage, 
or an interchange of the origins of the sartorius. 



propelling forces alone are called into play, and every muscle "of the 
line " has to contribute its part, and the action is automatic. 

The muscles not employed as propellers or carrying weight are 
few and small, as we have seen, bearing no comparison to the others. 
We will consider the latter in their order, commencing with the great 
glutens (Plates III., IV., V., c, c, t,). It is a muscle of the first rank. 
As seen in the plates, it reaches forward over the loins and adheres to 
the strong aponeurosis, or tendinous membrane overspreading the ilio 
spinalis. It passes over the concave border of the ilium, or ridge 
between the hip and the angle of the croup, covers the upper surface 
of the ilium and the ligaments that cover its openings, and is at- 
tached to the spines of the lumbar vertebra and those of the sacrum ; 
it is also attached to the strong aponeurosis that covers it externally 
like all superficial muscles of the back. This aponeurosis is repre- 
sented as dissected away in the plate. Its fibres all converge outward, 
downward, and backward to their insertion into the great trochanter 
behind the head of the bone, best represented in Plate V., c, c, c. (The 
great trochanter is so largely developed that it forms the short arm of 
a lever, bent at almost a right angle to the shaft of the bone, whose 
length does not exceed four inches from the head of the bone as a 
fulcrum.) The length of its longest fibres is twenty-six inches, and 
its average weight in two well-bred mares * was found to be sixteen 
pounds. It occupies a very advantageous position to give speed to the 
movements of the leg. The length and volume of its muscular fibres 
enable it to keep up a sustained action from the time the hind foot 
takes the ground under or in advance of the centre of gravity, until 
it leaves it after completing its propulsive effect. When the foot is 
off the ground it furnishes the sinews of war, offensive and defensive. 
The distance from the insertion to the fulcrum or head of the bone 
being so short, it causes the foot when free from the ground to move 
with great velocity. 

The weight of the animal from which the measurements and weights of muscles are given 
was about 1,100 Ibs. These figures must not be considered absolutely correct, but relatively. 
In a horse regularly worked the muscles will be found to be heavier than in the better bred but 
idle ones sacrificed on the altar of Science. 



If the reader will refer to Plate III. he will see only a portion of 
this muscle ; its extent forward is concealed by the pearly-colored apo- 
neurosis which completely covered it and is only partially dissected 
away; and by comparison with Plate VIII. and the skeleton, Plate II., 
he will find little difficulty in understanding the relations of this muscle 
with the surrounding parts. In the 'succeeding Plate IV. the whole 
outer face of it is exposed except the extreme posterior border, which 
is covered by the long vastus muscle crossing its fibres diagonally; the 
concavity in the ridge of the ilium from b to g, Plate VIII., shows also 
the aponeurosis which covers the ilio spinalis and which serves as 
a base for the attachment of the gluteus forward of the ilium. At 
Plate V., h, are seen the attachments by tendon of the great gluteus to 
the trochanter. (See skeleton, Plate II.) The centre of motion, or 
head of the femur, for the posterior limb is a little in front of this, lies 
deeper, and cannot be felt externally. This trochanter, therefore, is 
relied upon by horsemen as a point for measurement, and is known to 
them as the " whirlbone." Referring again to Plate VIII., the severed 
tendons of the great gluteus may be seen at c, c. 

The deep gluteus is well shown at P, Plate VIII. It arises on 
the shaft of the ilium, and its fibres follow the course of that bone and 
adhere to it as they descend. Its muscular fibres are intermingled 
with tendinous bands following the same course, and the insertion of 
the muscle is into the neck of the femur, or thigh bone, just outside 
of the capsular ligament. Its curious construction of mingled bands 
of tendon and muscle gives it the properties of both, the passive re- 
sistance of the former and the active aggressive force of muscular fibre. 
The spiral course of its fibres indicates that it is intended to rotate the 
leg outward, but more especially to hold the head of the femur in its 
socket. Its influence in locomotion must be small. 

The long vastus is second only to the great gluteus in weight, 
its equal in length, and from its great advantage of position much 
superior to it in effective power to perform the work required of 
it. Its position may be seen in v, Plates III., IV., IX., and in Plate 
V. its absence is more conspicuous than its presence could be. Its 
insertion is into the external condyle of the femur (see Plates II. 





and V.), and its relations are so perfectly shown in the plates as to 
scarcely require description. Plate IV. shows the superficial gluteus 
removed and the anterior margin of the long vastus exposed. It 
has its origin on spines of the sacrum posterior to those occupied 
by the superficial gluteus ; it fills the deep fossa anterior to the 
tuberosity of the ischium, and overlaps the hip joint four inches ; 
being lodged in this deep fossa, its position is fixed at that point; 
its direction is then changed so as to run downward and forward 
until it reaches the lower end of the femur, where its tendon is con- 
founded with that of the patella. 

.\s thus described, the posterior branch, which is admitted by 
anatomists to be distinct in structure and function, is detached. (It 
is marked s' in Plate V.) This is done for reasons which will be 
given when we come to consider the semi-tendinosus. Its weight,, as 
so limited, is nine pounds, its length twenty-six inches. The space 
occupied on the surface in front of the tuberosity of the ischium 
is eight inches, or four inches over the trochanter of the femur, and 
the circumference of the body of the muscle at that point is fifteen 

It is nearly uniform in thickness throughout, except as its mus- 
cular fibres give way to tendinous ones toward its lower insertion. 
While the great gluteus has some of its fibres measuring as long, the 
great mass of them, on which its strength depends, are not half that 
length. The concentration of the fibres of the gluteus before their 
insertion into the trochanter is very great, and as their power depends 
upon their number and not upon their length, that of this muscle is 
enormous. Though it acts on the short end of the lever, the line of 
its action is very direct. But the vastus acts upon the extremity 
of the long end of the lever, and from the great length of its fibres 
sustains its action for a long time. These muscles hold a very 
interesting relation ; they supplement one another. The power of 
the gluteus is effective in giving velocity, as in kicking; that of 
the vastus is effective in pushing the body over the foot on the 
corresponding side, when it is fixed upon the ground, as in rearing 
and leaping ; in the hare, whose mode of progression is by a sue- 


cession of bounds, it is developed enormously in comparison with 
the gluteus. 

The semi-tendinosus is represented in Plates III., V., IX., s, s, s, 
where its situation is shown immediately behind the vastus. It 
has two origins, one from the sacral spines and the first of the tail 
bones or their ligaments, the other from the lower face of the 
ischium (Plate V., i), below which they unite. It divides into three 
branches; the central is attached to the strong fascia covering the 
muscles of the calf, the other two reach forward to be attached to 
the same common fascia, one on the inner and the other on the 
outer face of the leg; the latter is spread out as far forward as the 
insertion of the long vastus ; the inner to a corresponding position 
on the inner face. These lateral branches overlay the muscles of 
the calf, or gastrocnemii, and give that compressed form that distin- 
guishes the calf of the horse's leg. It is a powerful muscle. Its 
weight is eleven pounds. The distance of its origin at the spine 
to its insertion at the head of the tibia is twenty-eight inches. 
The part of the muscle which has its origin at the ischium, to the 
same point of insertion, is nineteen inches, and its greatest circum- 
ference is ten inches. 

The action of this muscle cannot be represented by any abstract 
terms. It has two functions : it lifts the leg when the act of 
propulsion is complete, flexing the leg upon the thigh until the 
line perpendicular from the centre of motion is passed, when it 
relaxes, while the extensor proper of the leg, the triceps femoris (/, /), 
carries the foot to a new position in advance. As soon as the foot 
is upon the ground and the limb feels the weight thrown upon it, 
then the full power of this muscle is called into play, no longer 
a flexor, and not as an extensor, nor even as a propeller, but as a 
supporter, which character it performs until the direction of its fibres 
passes the perpendicular, when they cease to act until the next stride 
begins, so that when the foot is off the ground in the first quarter 
of the stride it is a flexor; it is inactive in the second quarter, 
and a supporter in the third, while it plays no part in the fourth. 
The importance of the proper understanding of the action of this, 



as of other muscles of the haunch, will be appreciated when we come 
to the consideration of the fast paces. 

The external branch of the semi-tendinosus has by all anatomists 
been claimed as the posterior part of the vastus, while it was admit- 
ted to be anatomically and functionally distinct. There is really no 
relation between them except in their juxtaposition and in their super- 
ficial appearance. Their connection is by a thin layer of cellular 
tissue, while the connection between the branch in question and the 
semi-tendinosus is most intimate, the partition being an aponeurosis 
to which both are attached, as in penniform muscles, from which it 
is impossible to separate the muscular fibres without laceration. I 
have no doubt that the point will be conceded by all anatomists when 
their attention is called to it, especially since it is shown that the 
annexation I propose makes a complete organ of the semi-tendinosus, 
with all its parts acting in perfect accord. 

The semi-membranosus adjoins the last-described muscle and is 
concealed by it in Plate V. Their relation is seen in the posterior 
view, Plate IX., /. This muscle also has two origins like the last, 
but that at the spine is by a thin tendon, and this branch is small 
(Plate VI., a). The great mass of the muscle (/, Plate VII.) arises 
from the lower surface of the ischium (Plate VII., c]. It is thin pos- 
teriorly where it overlaps the semi-tendinosus (at /, Plate IX.), but be- 
comes thick where it unites with the so-called great adductor (g, Plate 
VII.). The lower insertion is broad, the posterior portion of it is into 
the fascia of the leg, and the anterior by tendon along with that of the 
great adductor into the interior condyle of the femur opposite that 
of the vastus ; its weight is six pounds. The thin posterior portion 
of the muscle acting on the fascia of the leg flexes it like the semi- 
tendinosus, but the great mass of it acts in unison with the great 
adductor (g, Plate VII.), with which it is so closely united that it is 
difficult to separate them. 

The great adductor also rises from the ischium in front of the 
last described, and is inserted into the internal condyle of the femur; 
its weight is three and a half pounds, and its fibres are fifteen inches 
in length, though fibres are thrown off along its course to the femur, 

4 6 


on which it acts as an adductor when the animal is at his ease, but the 
joint action of these two muscles is as supporters. They have no 
attachments forward of the centre of motion at the head of the femur, 
but like the semi-tendinosus they permit the limb to be advanced to 
the extended position to support the centre of gravity, and then, in 
common with all the great muscles of the posterior extremity, they 
support the whole weight of the body, and then only for a limited time 
do they act as extensors. This will be better understood when we 
analyze the movements in the gallop. 

There is only one other muscle of the thigh which we will notice, 
\hzgracilis (Plate VI., m). (It is dissected away in Plate VII.) It is 
superficial on the face of the thigh, and is nearly as broad as it is long. 
It has its origin on the symphasis of the pubis where it meets its 
fellow of the opposite side. It is about an inch in thickness in the 
centre, thins off each way, and is attached to the fascia of the leg 
for a distance corresponding to its origin at the pubis. It corre- 
sponds to the gracilis in man, and is called by Chauveau the short 
adductor. Its weight is about two and a half pounds. The course 
of its fibres is downward and about five degrees outward. In its 
contraction the force is as an adductor about ten per cent, but as a 
supporter to the weight of the body when it rests on one foot its value 
is not to be overlooked. 

The want of knowledge of the action of the limbs in locomotion 
has led the student of anatomy into a too circumscribed view of the 
action of the muscles. It has led him to give first consideration to 
forces of secondary importance. It will be seen by a general view of 
all the muscles of the haunch that those acting upon the thigh bone, 
or femur, from above are inserted on the outer face of the bone, while 
those from the lower surfaces of the pelvic bones are inserted into the 
inner face of the femur. The primary object in both is locomotion, but, 
from the indirect manner of the application of the forces, they are all 
necessarily compound ; for example, the great gluteus acts as a pro- 
peller and adductor, while the great adductor acts as a propeller and 
adductor, the Eduction of one being compensation for the seduction 
of the other. In a humanly constructed machine, as a locomotive, 






where the angles are right angles, and the application of power is direct, 
there is less need of composition of forces ; but the design of nature 
was higher: beauty was superadded to power, and for this end great 
sacrifices of power were made. Though difficult of demonstration, it 
may be taken for granted that at full speed the adduction and abduc- 
tion of all the muscles in action counterbalance each other; if they did 
not, either the feet would interfere or they could not be brought to 
support the centre of gravity, and in either case the animal might fall. 

How is it possible for the student to learn the action of the machine 
when the muscular forces are represented as chiefly composed of 
adductors and abductors, as if the animal was designed to move side- 
wise like a crab ? These names may be perfectly proper to express 
the action of their analogues in man ; for man, of all his relations, has 
the most inefficient locomotive apparatus, but the greatest diversity of 
action in his extremities. 

Leaving the muscles of the haunch, we descend to those of the leg. 

The triceps fcmoris (Plates III., IV., V., IX., /, f) is the great 
muscle that occupies the front of the thigh. As its name implies, it 
has three heads. The middle one has its upper insertion in the 
smooth facet of the pubis, directly above the acetabulum, or cup, in 
which the head of the femur rests (Plate II., 6), and is called the 
rcctns. The other two heads are attached to the broad face of the 
femur, as close as possible to the head of the bone without inter- 
fering with its free action. Its length is eleven inches only, but 
its circumference is twenty, and its weight nine pounds. It cannot 
parated into distinct muscles, and it acts as a unit in extend- 
ing the leg forward through the patella, or knee cap, its point of 
insertion ; but the rectus, or middle head, being attached to the pel- 
vis, has the power of moving the femur on which it lies, as well as of 
extending the leg in common with its fellows, so that the action is to 
extend both bones on a line forward ; but the patella is not, like that in 
man, a part of the knee, or articulation, between the femur and the tibia; 
it has a place of its own. The front portion of the lower extremity of 
the femur is elevated or built up, and furnished with a trochlea, or 
grooved surface, with cartilage and synovial membrane, expressly for 


the patella to play on as over a pulley ; the tendon of the triceps, after 
being inserted into the patella, is extended beyond it to be inserted into 
a rough tubercle in the head of the tibia. Anatomists call the portion 
below the patella, ligament. Physiologists may say that the patella is 
developed in the tendon. We will not discuss the question. It is to 
us as if , the bone was developed in the tendon as it is developed in ten- 
dinous fibres elsewhere, and the ligament below the patella does the 
same office as the tendon above. The force of this powerful muscle 
as determined by its circumference can only be compared to the great 
gluteus, and is called into action after the extreme of flexion has been 
passed, and the femur has been brought forward by its flexors already 
referred to, and in which the rectus may have borne a part. After the 
foot has taken the ground it steadies the stifle, or knee, and regulates 
the flexion of that joint as the angles close to shorten the limb. After 
the perpendicular is passed, it again resumes the offensive and extends 


the leg in giving the propulsive impulse, which it maintains to the 
close of the stride. It rests, therefore, but for one fourth of a stride, 
and if the rectus acts as a flexor of the thigh at the same time with 
the flexors of the thigh upon the pelvis it has but little rest. 

The gastrocnemii (Plate VIII., in, m), or superficial muscles of the 
calf, hold a corresponding position on the leg to that of the triceps on 
the thigh, as well as to the levers on which they act; but while the 
action of the triceps is very simple and easily comprehended, that of 
the muscles of the calf is very complicated, and can only be understood 
by a study of the whole limb as a machine of which the voluntary 
muscles form a part. Whether it will be possible for me to interpret 
the action of the muscles and the use of the tendons with their checks 
and reinforcements without the actual limb before us is a question to 
be determined. An attempt was made to represent the parts by the 
aid of the camera, but the results were not satisfactory. Plate X. is 
from a careful drawing by Hahn. The gastrocnemius of the right side, 
g, is dissected away from its origin in the femur and raised by hooks 
to show the perforatus tendon,/. This tendon is inserted into the 
femur about two inches from the joint, along with the gastrocnemii 
muscles. It has a muscular body of its own, not distinguishable in 



the drawing, being there confounded with the body of the muscle lying 
upon it. On their way to their insertion into the point of the hock the 
tendons of these two muscles are twisted upon each other half round, so 
that the pcrforatus tendon, which was beneath, reaches its insertion at 
the outside of that of the gastrocnemius. The tendon of the latter is 
fixed immovably to the bone, and acts to extend the metatarsus below 
it, but the tendon of the pcrforatus passes over the point of the hock, 
where it is provided with a pulley similar to that at the knee, over 
which it glides to a very limited extent, being strongly secured by liga- 
ments to the point of the hock, /i; it then passes down behind the 
metatarsus, or cannon bone, to the pastern, or fetlock joint, where it 
throws out a ring to encircle the tendon of the perforans, as seen at 
r. (These two tendons, forming the " back sinews," would be liable, 
from the extreme flexions and extensions which take place at that 
joint, to be dislocated, but for the extraordinary provisions made to 
prevent it.) It then passes to its insertion into the bones of the foot. 
When the knee is flexed, as in the plate, this tendon (perforatus), 
being inserted into the femur above the knee joint, is relaxed, and the 
extensors of the foot, which are located in front (a), are permitted to 
straighten or extend the foot, as may be seen in all the plates where 
the hind foot is in the act of taking the ground ; but when the leg is 
extended upon the thigh the tendon is drawn upward, and flexion at 
the joints of the foot is effected, the extensors at a offering no oppo- 
sition, so that extension of the superior joints, as in the act of propul- 
sion, causes flexion of the inferior. This movement is independent 
of muscular action, and may be shown in the dead subject, except so far 
as the act of the extensor of the foot (extensor pedis, a), is concerned ; 
but the spindle-form body of the perforatus muscle connected with the 
tendon contracts by volition, and flexes the foot with its added force. 

If we consider the limb in the position as given in the plate, and 
then forcibly extend the foot until the pastern joint, S, is in the posi- 
tion it takes when the horse is standing, the tendon, /, will become 
tense, and also the ligaments that limit its motion at the point of the 
hock,//; beyond that it cannot be moved by any force that we can 
apply short of breaking. It is tied by the ligaments at the apex of 


the hock; and if the knee and hock joints are both extended it will 
not change the relations, for the tendon, c, m, and the shaft of the 
tibia, n, k, being parallel, and the distance from the hock joint, n, to 
the apex of the hock, c, and that from the centre of motion, /, at 
the knee to the insertion of the tendon at the femur, m, being equal 
and parallel, they form a parallelogram, and changes in the angles, 
as in flexion and extension, will not affect the length of its sides. 
When the knee or the hock joint is flexed or extended, the other 
must follow. When the horse is standing, and the knee joint is ex- 
tended, as well as the hock, the horse rests mechanically upon the 
tendons, but the knee is extended by the triceps, b, whose tension 
requires an effect of the will and tires in time, so that we see him 
when at his ease rest on his hind legs alternately, which he never 
does with his fore foot, except when one of them is lame. 

The perforans muscle, which is so intimately related to the last 
has its origin below the knee joint and on the upper and posterior 
face of the tibia and fibula, below the popliteus (Plate X., e\ and its 
action is not influenced by the flexions of that joint. Its tendon takes 
a more direct course to its insertion ; it passes through a groove at the 
base of the calcaneum, near , on its inner side and as near the joint as 
possible. Strong ligaments cover the groove where the course of the 
tendon is changed, to prevent its displacement. It then passes down 
behind the metatarsal bone and inside the tendon of the perforate 
On its course it receives the tendon of another small flexor, and fror 
the posterior surface of the metatarsus an auxiliary tendon or ligament 
of nearly its own size. In the plate this branch is shown relaxec 
The tendon, thus reinforced, is of twice the size it was before the 
union, and passes above the pastern through the ring, r, of the perfc 
ratus, and is inserted into the bones of the foot. 

This muscle, being entirely independent of the femur and the 
muscles attached to it, may flex the foot independently, and does so ii 
propulsion in the last part of the stride, and also in the same contrac- 
tion aids by its pressure at the back of the hock in extending that 
joint, thus extending one joint while it flexes another. When the foot 
rests in the standing position, the auxiliary tendon, t, above mentioned 


converts the part below it into a continuous tendon, which performs 
the office of a ligament, in common with that of the perforatus, to 
aid the suspensory ligament in supporting the weight of the body in 
the extreme extension which the pastern undergoes when the centre 
of gravity is over it, as in rapid locomotion. 

Muscular fibres are found by anatomists scattered through the 
tendons below the hock ; but for all mechanical purposes the sources 
of power are above and away from the extremities, where the velocities 
are, at times, more than twice that of the body and the momentum 
must be arrested at every stride. The hock in quadrupeds represents 
the heel in man, and the elongations of bones and corresponding 
tendons are necessary modifications of the plan for the development 
of speed. 

There is a group of small muscles which form what is called, by 
some horsemen, the second thigh ; they are on the outer face of the 
thigh and below the stifle, or knee, and in front of the calf. The 
perforans (d, Plate X.) is in this group, occupying the intermediate 

The flexor of the metatarsus has its upper attachment on the 
tibia, in front of the perforans, and its lower in the metatarsus, below 
the joint, after passing under the annular ligament. It is minutely 
described by Chauveau. It flexes the hock joint and is a feeble an- 
tagonist to the gastrocnemii, but only acts when the foot is off the 

The lateral and anterior extensors occupy, as their names indicate, 
spaces on the tibia in front of the latter, and their tendons, after passing 
under the annular ligament, in front of the hock, descend to be in- 
serted into the anterior face of the foot ; they act, therefore, to flex the 
hock and extend the foot, raising the toe as the limb is thrust forward 
to take the ground. 

The suspensory ligament is one of the most wonderful contrivances 
in the whole locomotive machinery of the horse. Though a ligament 
only, with its action beyond the control of the will, it is no less an active 
organ, whose function is indispensable to locomotion, and the interest 
in it has been much increased by the developments of the camera. 


It is not necessary, in order to consider the relations and functions 
of this organ, that we should enter into a detailed account of all the 
ligaments of the foot; they are very numerous. Anatomists limit the 
name to the strong band that has its upper attachment to the meta- 
tarsus below the hock, and its lower one into the sesamoid bones, and 
they have given the name of sesamoid ligament to that continuation 
from those bones to the foot. We will not discuss with anatomists the 
question of their identity, but, mechanically considered, they arc one, 
and, like the patella, the sesamoid bones may be said to be developed 
in the ligament. If the name were limited to the first, it would be a 
misnomer; for, to suspend the weight that is thrown upon it, it is 
necessary that a counter force should act upon the opposite border of 
the sesamoid bones equal in strength to that above it. If either part 
were divided, the other would have no function, but united they con- 
stitute an instrument that often bears the weight of the whole body. 
It is a broad, thick band, resembling tendon, and may be felt above the 
fetlock between the splint bones and the tendons of the perforatus 
and perforans or " back tendons." This ligament fixes the sesamoid 
bones in the position above and behind the articulation of the first and 
second metatarsals, so that when the second metatarsal or pastern 
bone is thrown out from under the first metatarsus they are drawn 
into its place, and, their articular surfaces forming an arc of the same 
circle, the loss of the pastern is not felt ; but the sesamoids now bear 
the whole weight of the body, and they have no support but the sus- 
pensory ligaments in which they are imbedded, and the tendons of the 
perforans and perforatus, which cross the bridge between the sesa- 
moids. The perfect equilibrium between the strength of the ligament 
and the force it is required to resist is of the utmost importance. 
When the horse is standing upon all four feet, the weight is equally 
distributed, and the angles formed by the pasterns with the bones 
above are small, for the weight upon each one is not great enough to 
spring it far; but in running, the whole weight in every stride is 
borne by each foot in turn for a short time, and the elasticity and 
strength of its suspensory ligament must be, with that of its reinforc- 
ing tendons, just equal to its requirements to support the body, for 


they are all placed beyond the control of the will. If it yields too 
much, the fetlock is liable to strike the ground ; if it is too rigid and 
it does not yield enough, there will be stiffness and a hobbling gait. 
\Ve shall have occasion to refer to this again when we analyze the 

There is no one fact, brought out by the experiments of Mr. Stan- 
ford with instantaneous photography, of more interest than the action 
of the suspensory ligament. 

When the horse is standing, it will be seen that the pastern forms 
an acute angle with the metatarsus. Its position indicates the length 
of the ligaments, and it is their resistance that prevents the further 
extension of the joint ; but in running and fast trotting, this ligament 
is put upon the stretch, when the limb is shortened by the weight of 
the body, to such an extent that the pastern is made to take a position 
at right angles to the metatarsus and horizontal with the ground. (See 
the plates of horses speeding, passim.) Elongation of the limb begins 
immediately after the perpendicular is passed, and as the fetlock was 
the last joint to reflex in shortening, so it is the first to recover its 
normal extension. This spring continues its action during the rest 
of the stride, straightening the fetlock joint as the leg becomes elon- 
gated after the passage over it of the centre of gravity, still sustain- 
ing the body with undiminished force until it leaves the ground, when, 
being relieved from the superimposed weight, the flexor muscles re- 
gain control ; and it is the reaction of these ligaments, with that of 
the flexor tendons acting as ligaments, that produces the quick move- 
ment, quicker than is possible in muscular contraction, which causes 
the feet to throw dirt ; it is effected after the weight is off the foot 
and the propulsive effort is complete. There is no muscular action 
en the foot until after the pressure is removed and the flexors regain 

It is an exceedingly difficult problem to determine the absolute, or 
even the relative, work performed by the different muscular powers 
employed in locomotion. There are many different elements entering 
into the calculation, that are impossible to be weighed. Muscles 
differ in quality as well as quantity ; some contain a larger proportion 


of cellular or fibrous tissue than others, and will have less power, other 
things being equal. For example, the glutens and vast us are coarse 
muscles capable of resisting external force, and therefore popularly 
believed to be strong ; but it is in a meaning corresponding to tough- 
ness, and that quality depends upon the amount of interstitial cellular 
tissue they contain, which tissue has no contractile property, and can- 
not originate motion; while the psoas and iliacus, having but little 
such cellular or fibrous tissue, have little power to resist external force, 
but have a larger contractile power as measured by the areas of their 

Muscles do not often have their force concentrated at both extremi- 
ties, but it is distributed over the face of their levers at different dis- 
tances and at different angles, as in penniform muscles, and nearly all 
others in a greater or less degree, and at different angles at each change 
in the position of the levers. Though we recognize the same general 
mechanical principles, we cannot apply the same mathematical rules 
usual in mechanics ; add to these elements of uncertainty the com- 
position of forces often in the same muscle, and we see how for- 
midable are the difficulties in the way of reducing animal mechanics 
to an exact science. 

But while we cannot accurately determine the forces in detail, we 
can in the aggregate. We see all these different and often antago- 
nistic forces united in their action around a common centre of motion, 
as the hip joint, to effect one result. There are certain general princi- 
ples, however, that we can deduce from the facts before us. In order 
that the foot shall reach the ground as far in advance as possible, to 
support the centre of gravity as early as may be, and as long as pos- 
sible, and that it may use its propulsive force later, it is necessary 
that it should be possessed of sufficient length ; but it is bearing a 
burden whose weight we will suppose to be a thousand pounds, and 
going at the rate of twenty miles an hour, and the momentum is the 
product of that weight multiplied by the velocity. This is a respon- 
sibility that could not be borne on stilts. The difficulty is overcome 
by so constructing the whole limb that it shall be extensible, thus 
having all the advantage of length without its disadvantage ; and the 


centre of motion is actually lowered several inches that its practical 
length may be increased. For this purpose the system of levers is 
iiM'd, which, by their flexion and extension, practically shorten and 
lengthen the limb. The acutcness of the angles at which these bones 
intersect each other is, therefore, an important element in the mechan- 
ical action ; the angles to be acute require long levers, and long levers 
-Mtate long and powerful muscles to "man" them. These quali- 
ties must be bred. 

Flexibility of articular ligaments may be acquired by early training 
and regular exercise, but the proportions of the body are inherited. 
Length of muscular fibres and acute angles of the levers on which they 
act, give sweep of limb, and strength depends upon the number of them, 
and the effective power of both depends upon the will or courage ; but 
all these qualities would be vain if the motion of the extremities were 
not so co-ordinated that their functions should be performed without 
interference one with another. 

When the speed of the horse is twenty-five miles an hour the rate 
of the hind foot in passing that on the ground is twice that, or fifty 
miles an hour. It is even greater than that, for the velocity of the foot 
in its stride is an accelerated one during most of the distance, and may 
be supposed to be most rapid midway. Now the movements of the 
posterior extremity on its centre are controlled by voluntary muscles, 
liable from various causes to be irregular, as they must necessarily be 
from the ever-changing centre of gravity which it is designed to sup- 
port. There would have been danger of one foot striking the other leg 
in passing, an accident technically called interference, but another 
danger still greater existed at the stifle from the blows that joint would 
be liable to give the abdomen in its extreme and violent flexions. It 
is the duty of the iliacus muscle to guard the abdomen from this vio- 
lence, and when it performs its office well, it gives the " stifle action " 
so much admired ; but while the upper end of the leg (tibia) is thrown 
out in this action, the lower end is correspondingly thrown in, and the 
foot would be still more so but for the unique construction of the hock 
joint. .The interlocking grooves of this joint are not direct, as in other 
hinge joints of the body, and as the corresponding joint in man is, but 


oblique, so that when flexion takes place at that joint, the lower ray 
is carried obliquely outward, and when the other leg is passed, and the 
extension takes place again, its action is reversed, and the foot is 
returned to the position required to support the centre of gravity. 
By this simple contrivance the danger of this accident is placed beyond 
the will of the animal, and in well-formed horses beyond the possibility 
of accident. Some horses circumduct the hind feet more than others, 
and in others the stifle action is most marked ; but it is not common 
to see both excessive in the same horse. 

There is often considerable difference in different horses in the 
length of the hock. The long hock gives the greatest power, for the 
reason that the leverage is greater; but what is gained in power is 
lost in speed. 

Sometimes there is a looseness in the articulations of the tarsal 
bones immediately below the hock joint, which, by their freedom of 
motion upon each other, enables the joint to become more extended, 
and the last effort of the gastrocnemii muscles is given with great 
advantage of mechanical power from the practical shortening of the 
arm of the lever on which they act, and from the ability the limb 
acquires of retaining its position upon the ground for a longer time. 
It is a point in some fast animals, but would be considered a defect in 
a draught horse. 

Having given a detailed description of the parts concerned in the 
motion of the posterior limb, and their action, I will now endeavor to 
show how the machine acts as a whole. If the reader has familiarized 
himself with the parts by reference to the plates, while he has followed 
the description, he will experience no difficulty ; but if he has not, it 
would be as well for him to pass over the rest of this chapter. The 
analysis has no reference to any particular gait or co-ordination of the 
limbs with each other, but it is confined to the action of one posterior 
limb alone, and it will be found to be the same in all the paces, differ- 
ing only in the degree of action according to speed. 

We will take for our guide the posterior extremity as it has just left 
the ground, after the act of propulsion is complete, and in the medium 
pace, the trot. 


In order to aid the mind in understanding the actions of the muscles 
upon their levers, the skeleton is mounted with movable joints, by 
which means we are enabled to adapt it to. every position required. 
By this means it is a comparatively easy matter for one to understand 
the action throughout (See Plates II., XIV., XV.) 

Retraction begins by the relaxation of the gluteus maximus, the 
vastus, semi-membranosus, and the great adductor. The triceps also 
relaxes, and the tibia is free to respond to the contraction of the semi- 
tt nclinosus lifting its lower extremity. The tensor vagina?, acting from 
the hip upon the knee, the psoas magnus, iliacus, and sartorius from 
the inner and upper wall of the pelvis, with the anterior branch of the 
superficial gluteus from the hip, all act in concert to advance the thigh, 
the knee becoming more flexed as it is advanced ; and with the knee, 
or stifle, goes the hock joint, by the relaxation of the gastrocnemii and 
the mechanical arrangement before described. 

The flexors of the foot act at the instant their tendons are released 
from the forced service as ligaments, and continue their action until 
the perpendicular from the centre of motion to the ground is reached, 
which marks the point of greatest flexion of all the joints. The flexors 
of the thigh, already mentioned, maintain their tension to keep the 
Imver extremity of the femur in its advanced position. The semi- 
tendinosus relaxes, while the triceps extends the tibia upon the femur 
already well thrust forward, and the muscles of the calf, acting on the 
point of the hock, extend the metatarsus synchronously with the feeble 
action of the extensors of the foot. The perforans and perforatus do 
not take part in this movement, as their action would counteract that 
of the extensor. In this order the foot takes the ground, the heel 
being the first to make the contact, and by its elastic frog it is pecul- 
iarly fitted to receive the shock. It will be observed, by reference to 
the plates, that the bones of the entire limb are at angles best adapted 
to meet the contact with the ground. The toe is raised to avoid trip- 
ping, and allow the elastic frogs of the foot to make the first contact. 

The instant of contact, when the foot is as far forward as possible 
to sustain the centre of gravity, marks a sudden change. The flex- 
ors of the thigh, the sartorius, tensor vaginae femoris, iliacus, and the 



anterior branch of the superficial gluteus, give way, while the weight 
of the body relieves the extensors of the foot. The function of the 
limb at this time is to support the weight of the body and prevent it 
from pitching headlong ; and to this end, with the exception of the few 
small muscles just mentioned, the entire mass of the muscles of the 
limb is called into action ; and now that the foot is a fixed point, the 
semi-tendinosus acts in unison with the others to take the weight of 
the anterior half of the body. This is the use of all the vast mass of 
muscular power developed in the haunches and long muscle of the back 
(ilio spinalis). In this manner there is no act of extension, further 
than the extension of the body upon the thigh ; it is not until tht 
centre of motion, or head of the thigh, has passed over the foot that 
extension is possible ; and then the nearer to a horizontal the directior 
of the force applied, the more effective it will be. When the limb is per- 
pendicular, the whole force is employed in supporting weight ; but when 
it is exerted upon the ground at an angle of forty-five degrees, one half 
of the force is spent in supporting weight, and the other in propulsion 
if it could be exerted horizontally, it is plain it would be exclusive!] 
spent in propulsion. From the time when the foot is planted ir 
advance, until the leg has passed the perpendicular, the force is alsc 
compound, a part being employed in supporting weight, and the other 
in resistance which must be drawn from the momentum ; this last is 
reduced to the minimum by the gradual giving way of the triceps anc 
gastrocnemii, and contraction of the great propellers of the hauncl 
especially the vastus, which forces the trunk over the supporting liml 
The act of propulsion by the vastus begins from the moment that the 
hind foot takes the ground and its contraction begins. The effect of 
the contraction of this muscle is to shorten the distance between its 
two extremities ; one of these extremities is attached to the lower 
end of the femur and the other to the spines of the sacrum behind 
the croup, but the course of the muscle is not direct (see Plate V.), 
being deflected at the head of the femur, and most so when the 
foot first reaches the ground. At that time it presses with most 
force against the articulation pressing it forward, so that it extends 
the trunk upon the limb and forces it forward in the same act. 


After passing the perpendicular, and the angles of the extremity are 
increased, the semi-tendinosus ceases to act, and the extension is con- 
tinued by the vastus, gluteus, triceps, and muscles of the calf, to the 
end of the stride. In the flexion of the limb that takes place as it 
shortens in order to give uniform support, and not be itself crushed, 
the flexion is effected by the weight borne, in which the flexors proper 
bear no part ; their action could have no other effect than to bring the 
body to the ground, but it is effected by the gradual giving way of the 
triceps and the suspensory ligament. 

It will be seen that but a small part of the immense power of the 
extensors, or propellers of the posterior extremity, is spent in the act 
of propulsion, even when the animal is in full motion, but in supporting 
weight; and as the extension of the leg increases and the burden is 
assumed by another limb, it is the better enabled to exert its propelling 
power. As the limbs are successively relieved of that duty by their 
alternates, they are in better position to exercise their functions as 

This analysis of the mechanism of the posterior extremity will be- 
come of importance when we come to apply it to the run or greatest 
speed of the horse. The reader who has not had the patience to fol- 
low us through the study to the end of this chapter will not be able 
to master the next, and we would advise him to pass it over, and take 
up the fifth chapter, where we will endeavor to apply the demonstra- 
tions contained in these two ; but such must take the facts on which 
the theory of motion is based for granted. 



THE anterior extremity furnishes a subject for the study of anirm 
mechanics of more interest even than that which has demanded our 
attention in the preceding chapters. 

There appear at first sight greater difficulties in the way 
human ingenuity in the application of mechanical power for propul 
sion to the anterior part of the trunk. The mind is led by the simili- 
tudes of comparative anatomy, and the popular hypothesis of evolu- 
tion from one common parentage, to look upon the anterior extrem- 
ities as limbs in progress of development into arms or tool-makers. 
The mind jumps, like the kangaroo, from the marsupials to the mon- 
keys, to the orang-outang, and then to man by such easy leaps that 
it is difficult to persuade one that he has advanced to his opinions 

without substantial 


To these causes must be ascribed th 


universal opinion of writers on the horse that the fore legs are 
merely supporters; and the latest and standard authority on the 
horse, in England, compares them to the spokes of a wheel, and asserts 
that their only functions are to support the centre of gravity and keep 
out of the way of the propellers, the hind legs. It will be apparent 
to the reader before the conclusion of this chapter, if it is not ,so 
already, that each limb is required to support the body and act as 
propeller in turn, and that the anterior one does more than its share 
of both offices.* 

It will be shown, when we come to analyze the fastest pace of 
the horse, that the strongest propulsive force of either of the legs 
is given with the anterior one in each stride ; indeed, it is so strong 
as to raise the centre of gravity several inches above the horizontal 
line of its motion. As the case now stands between the anterior 
and posterior extremities, they may be compared to a peasant and 
his wife in certain foreign lands, in which the latter is required to 
share equally with her husband in all his labors and also to bear 
burdens which he cannot share with her. 

The beautiful contrivances by means of which the anterior limb 
is enabled to support weight as a crutch, to be acted upon as a 
passive instrument in propulsion, and at the same time to consti- 
tute an autonomy of its own, independent of both the others, for the 
accomplishment of the same general result, cannot fail to excite the 
most profound admiration, and wonder that its mechanism has not 
been better understood. 

On reference to Plate IV., s, one will see the posterior half of 
the great serratus brought into view by the removal of the superficial 
muscles that hide it in Plate III. It is so called because its lower 
border is serrated or notched, the lower attachments being to the 
first eight ribs ; the anterior half of the muscle is concealed by the 
shoulder. This muscle is fan-shaped, its fibres converging upward 

* Mr. Walsh (Stonehenge) gives the authority of M. Baucher for the statement that 
the weight borne by the anterior and posterior extremities, as determined by placing them 
upon different weighing-machines, was as 210 for the former to 174 for the latter, the total 
weight of the horse being 384 kilogrammes. 



to a common centre on the inner face of the upper border of the 
shoulder-blade, or scapula, as seen in Plate XL, .$, s. 

When this muscle is recently exposed it presents delicate nacre- 
ous tints rivalling pearl. The artist has suggested them only in his 
drawing. This pearly coat of the muscle is tendinous in its struc- 
ture, and extends over the whole exterior surface of the great serra- 
tus. These tendinous fibres extend throughout the muscle, but are 
in greater proportion near the centre or long axis (Plate XI., a). 
These tendinous fibres, concentrated at a, mav be considered the 
centre of motion for the whole limb when supporting the weight of 
the body, whether acting alone, or in conjunction with one or more 
of the other limbs, and whatever may be the direction of its axis 
with reference to the trunk ; but this centre of motion must not be 
confounded with the centres of motion existing in the joints ; it 
holds a corresponding position with the " whirlbone," or hip joint 
of the posterior extremity. This intermixture of muscular and 
tendinous fibres existing in this muscle is found in others, as the 
deep gluteus described in the last chapter, enabling it to perform 
the functions of both muscle and ligament. The tendinous fibres 
which are in the greatest proportion in the long axis, when put 
to their tension absolutely limit elongation to that degree, and ar 
useful when the animal is standing ; as these tissues are incapable 
of fatigue, so he has no occasion to rest them. With the aid of 
another muscle, which we shall describe further on, having the same 
characteristic construction as the serratus, the horse is enabled to 
stand in his stall all day without resting either of his fore legs ; 
while in the hind leg the labor falls upon the triceps (Plate IV., /), 
of pure muscular fibre, and he will be observed to rest his hind legs 
alternately. (See page 50.) 

The muscular fibres of the serratus are most abundant at the 
anterior and posterior borders. The former aid in preventing shock 
when the foot first takes the ground, and the latter in giving the 
final propulsive effort when it leaves it ; and by their joint action 
they relax the tendinous fibres, or bands, which, being passive, have 
no such power in themselves. 






The centre of motion in the anterior extremity may, in its 
mechanical function, be considered as a joint, and the only kind of 
joint possible in that position; were it constructed like the corre- 
sponding joint in the posterior extremity, it would be inevitably 
broken by the contact with the ground, thrown out as it is in 
advance of the centre of gravity. For the same reason it is not 
provided with a collar-bone, or clavicle, as in man and the anthro- 
poid animals, in whom that bone fixes the shoulder and makes it 
the centre of motion for the limb. 

On reference to Plate IV., s, the great serratus will be seen as a 
fan-shaped muscle which has its lower attachments spread out over the 
first eight ribs. From the attachment to the different ribs its lower 
border is like a saw, from which its name, "serratus." The artist 
has vainly attempted to represent the nacreous color, in which it vies 
with the mother-of-pearl. This is the tendinous covering to the 
muscle, and it is much intermingled with tendinous fibres, which 
limit elongation and take the strain from the muscular fibres when 
their contraction is not called for. The upper attachment of this 
muscle is on the inner face of the scapula, or shoulder-blade (Plate 
XI., (?), below the cartilaginous border, with the dark line mark- 
ing the boundary between it and other muscles. In the centre 
are seen the gray fibres of tendon, which are continuous below, 
and enable the animal to rest the muscular fibres and limit their 
elongation. The space covered on the inner face of the scapula is 
nine inches in its greatest measurement by two in its least. 

The space below the section of the serratus, as seen in s, s, 
Plate XL, and between that muscle and those of the inner face of the 
shoulder-blade, is lined with loose cellular tissue, which, while it con- 
nects the opposing surfaces, allows of unrestricted motion upon the 
centre, a, and prevents friction. The body in a standing position 
rests the weight of the anterior half upon these serratus muscles as 
upon a sling to which the anterior extremities correspond to crutches. 
. But when the foot of one of these limbs is off the ground the 
serratus is relaxed, and the limb would drop but for another set of 
muscles, which, though feeble, are sufficient for the purpose which 


they serve. This is the special function of the trapezius (g, g, 
Plate III.). It is so perfectly represented in the plate that it requires 
but little description. It is divided into two parts by the spine of 
the scapula (see Plate II.), into which both divisions are inserted 
along with a band of the ligament of the neck, which seems to be 
sent off for the purpose of aiding with its passive force the trape- 
zius in holding the limb to its place. The upper insertions or origins 
of both divisions are in the same ligament of the neck, or yellow cord, 
as it is well called by hippo-anatomists. This cord is distinguished 
not only by its color but by its elasticity from all other ligaments. 
It seems to be, indeed, a special contrivance to afford means for the 
attachment of important muscles when the spines of the vertebra 
are too remote to afford it. It extends from the head to the strong 
spines of the dorsal vertebra, where it becomes merged into ordinary 
ligament. It may be that the branch of this cord that is inserted 
into the spine of the scapula is itself sufficient to support the weight 
of the anterior limb, and that the muscle under consideration is used, 
the two parts acting alternately, to aid in locomotion, exerting their 
forcj at the upper or cartilaginous extremity of the scapula and above 
the centre of motion or attachment of the serratus ; but however that 
may be, its aid in locomotion cannot be great, as its entire weight 
does not exceed two ounces. Its thickness does not vary much from 
half an inch. It is separated from the skin only by the general 
aponeurosis, or fibrous covering described in a former chapter, and 
which has been dissected away from the whole body in the subject 
of the drawings. 

When the trapezius is removed, the rhomboideus is brought into 
view. This muscle is so named from the corresponding muscle in 
man, in whom it is in the form of a rhomboid ; and if the name were 
limited to the muscle so far as it corresponds to that in man there 
could be no objection to it, but since Cuvier's time it has been made 
to embrace another muscle, the levator anguli scapula (Plate IV., /) 
To this union in the horse there can be no objection, anatomically 
or mechanically; but when so united they are no more like a rhom- 
boid than a tent-pin, and the name of levator anguli scapulae should 


have been applied to the united muscles, if either; but the worst 
part of the history is that the name of levator anguli scapula? was 
applied to another muscle, the trachclo subscapularis (Plate IV., g, g). 
No name could be more inappropriate than this; in no way, directly 
or indirectly, can it be said to lift the angle of the scapula, as may be 
seen by reference to the plate. The function of this last-named mus- 
cle has, so far as I know, never been understood until now, and will 
be explained further on. But this furnishes another example of the 
confusion arising from hippo-anatomists being misled by human anat- 
omy. The levator anguli scapulas is quite distinct from the rhom- 
boideus in man, having its origin in the transverse processes of the 
vertebra of the neck, while in the horse its origin is in the spinous 
processes of the vertebra, as far back as the withers and along the 
yellow cord. (See Plate IV.) In man, its name, lifter of the angle 
of the scapula, is good, for that expresses its function ; in man, 
however, it is no locomotive organ, but even more necessary to 
the complicated movements his superior extremities are required to 

From the necessity which exists, for the reasons given, of restoring 
the old name to the trachelo subscapularis, the restoration of the 
name levator anguli scapulae to its old association becomes necessary, 
if it is not to be abandoned altogether. In order to make intelli- 
gible a description of the mechanical action, there is need of definite 
terms, and we will apply the name levator anguli scapulae to include 
the rhomboideus as well. 

The contraction of its fibres does not take place until the leg is 
extended and the foot rests upon the ground ; it then acts to draw 
forward the tipper or short end of the whole extremity as a lever 
with its fulcrum on the ground and its weight at the centre of motion. 
The course of its fibres is accurately drawn in the plate, the limb 
being in its normal position. Its posterior fibres are few, but as it 
extends forward they become numerous and more powerful. Their 
insertion is into the inner border of the cartilage (Plates IV. and XL, 
, , ;/); at the anterior border, ', is the insertion of the muscle known 
before the time of Cuvier as the levator anguli scapulae ; they form a 



considerable mass, and join on to the serratus, s, so nearly in the 
line of the centre of motion that it may be that they act in con- 
junction with the trachelo subscapularis, whose insertion is at g, 
Plate XI. 

The last-named muscle is well exposed in Plate IV., g, g. As 
there seen, it is triangular. It arises from the transverse processes of 
the last six cervical vertebra, and its fibres converge to their inser- 
tion on the inner face of the scapula, in front of the insertion of the 
serratus, or centre of motion. Its muscular fibres are in little fasci- 
culce, or bundles, separated by interstitial fibrous or cellular tissue, 
to admit of great freedom of motion upon each other in the extreme 
vertical flexions of the neck while grazing. It is a powerful muscle, 
its weight being three and a half pounds ; but its action has not been 
comprehended, its fibres being nearly horizontal on an average, or a 
little upward, and their insertion on a line with the centre of motion ; 
it can have no active agency in locomotion, though with the joint 
action of the levator anguli scapulae it may move the upper end of the 
scapula forward, as far as permitted by the tendinous fibres of the 
serratus and the branch from the yellow cord ; but that cannot be 
much. Until the theory of quadrupedal motion was understood its 
function may well have been overlooked. It is now clear. Its attach- 
ment being on a line with the centre of motion and directly upon a 
fixed point, it cannot be supposed to aid in the motion of the scapula 
about that point; but when the animal is running, and the fore leg 
is thrown forward and takes the ground, it is required alone to 
receive the weight of the whole body or be itself crushed by its 
momentum. This will be resumed after the action of the triceps 
brachii at the same instant is shown. It is sufficient for the present 
that the action of this muscle abstractly be understood and remem- 
bered. Its general appearance is so like the muscle above it, the 
scale nus (m, m, m), having similar origins along the cervical ver- 
tebra nearer the head, and its insertions into the spines of the dorsal 
vertebra (hidden in the plate by the overlaying levator anguli scap- 
ulae), that it is apt to be confounded with it; but the scalenus is 
not a locomotive muscle, its function being to raise the head when 


the pair act unitedly, and to bend the neck laterally when each 
muscle acts separately. 

\Ve have shown how the anterior extremity is used as a supporter 
to the trunk, or crutch, and how it is itself supported in its position 
when not so acting. The mechanical principles involved are very 
simple. The method in which mechanical power is applied to the 
same limb as a lever in locomotion will be found to be no less so, and 
if the contrivance does not display as great ingenuity as some parts 
of the locomotive organs, it is because there was no occasion for such 
display : it has the merit, at least, of being very primitive. 

\Yhile there is no bony connection between -the anterior extremity 
of the horse and its trunk, therefore no fixed point of resistance 
and reaction, as in the posterior extremities, the centre of motion is 
attained equally well, and it is difficult to conceive how it could serve 
its different relations to the trunk any better. The centre of motion 
in the anterior extremity is in the scapula, as high as a bony base could 
be reached. This, if not anatomically so, is mechanically a joint, and 
corresponds to the hip joint of the posterior extremity, the shoulder to 
the stifle, and the elbow to the hock. In this view, there is no reversed 
order in the joints, as has been stated, but the same mechanical relation. 
The freedom of motion at its centre in the limb is less than in the 
corresponding joint in the posterior extremity, but there is all that 
is required ; it is placed considerably higher than in the latter, in 
order that more motion should not be required ; and the restriction 
at that point is compensated for by the superior flexibility of the lower 
joints. The total result is that the stride of one limb is just equal to 
that of the other. 

The limb, acting as a lever of the third order, having its centre of 
motion as high as possible, should have the power to move it applied as 
low down as possible, within the periphery of the body ; but the farther 
from the fulcrum, or centre of motion, the power is applied, the greater 
will be the space moved over, and, consequently, the longer must be 
the fibres of the muscle.* This requisite is furnished by the great 
dorsal (Plate III., d, d), which has for its base the spines of the last 

See page 31. 


fifteen dorsal and the lumbar vertebra. Though spread over so much 
space, the muscular tissue is not correspondingly extensive. The pur- 
pose was to gain advantage of position as far back as possible to give 
the most direct action in the line of motion to be produced. As the 
fibres of its thin tendon (Plate III., /,/") converge forward and down- 
ward, they become more muscular, and most so just behind the scapula, 
which is covered at its posterior angle by it, and it is covered in turn 
in the same region by the dorsal division of the trapezius, g ; after pass- 
ing beneath the muscles of the shoulder (as seen in Plate XL, d,) its 
fibres again change to a thin, flat tendon, which unites with the tendon 
of the muscle, f, and is inserted with it into the internal tubercle of the 
humerus, about one third of the way from the shoulder to the elbow. 
If this muscle acted when the foot is off the ground, it is plain that it 
would flex the shoulder; but its function as a propeller is called into 
play when the foot is the fixed point, and the limb is supporting the 
weight of the body, and its articulations are all set. Under such con- 
ditions it forces the body forward over the foot; but its power as a pro- 
peller is second to that of the great pectoral (Plate III.,/, p). The 
limits of this muscle are a little in doubt. It is represented in the 
plate with the boundaries as given by Chauveau, but it is confounded 
so closely with the superficial muscle of the skin (paniculus carnosus) 
on its upper border that it is difficult to separate them. For our 
purpose, it is sufficiently shown in the plate, extending from the tenth 
rib over the thorax, covering the serratus magnus as high as the lower 
border of the great dorsal, and as low as the middle of the thorax, 
where it unites with its fellow of the opposite side. Its fibres con- 
verge as they are directed forward, and form a mass of muscle between 
the arm and thorax so great as to be second in power to no other loco- 
motive muscle in the body. Its insertion is into the inner tubercle 
of the head of the humerus, as seen at p, Plate XI., as near to the 
shoulder joint as possible. The great dorsal may perform two func- 
tions, flexion or propulsion, as mentioned. The muscle now under 
consideration has but one. Acting directly upon the angle of the 
shoulder, there is no loss of its immense power by indirect force, and 
from the moment that the foot touches the ground, its power is felt in 


forcing the body over it. As there is no loss of force in indirect 
action, so there is none spent in adduction or abduction, or in sup- 
porting weight ; that office is performed by the muscles of the limb 
acting automatically, and the effect of its traction upon the shoulder 
is to support it and prevent it from giving way while the limb is 
playing its independent part in sustaining the superimposed weight 
of the body. 

There seems no room for a doubt that the conjoined action of the two 
sets of muscles last described is the most powerful propelling force in 
the whole locomotive organism of the horse. To make this apparatus 
complete, there was necessary some force to return the limb to its posi- 
tion forward when the act of propulsion was completed. This force is 
found in two sets of muscles, the masloido humeralis and the superficial 
pectoral; the former has its fixed insertion at the mastoid process of the 
temporal bone, or base of the skull, behind the ear, and to the first four 
cervical vertebra.* It is shown in Plate III., m, m, m, passing downward 
and backward along the whole length of the neck and over the point 
of the shoulder, enveloping it, and is inserted at the humerus, about 
half-way from its two extremities. (See Plate IV., i, where the muscle 
has been cut away from its tendon of insertion. It is also severed at/, 
leaving only its upper portion in situ.) It is six inches in width where 
it envelopes the shoulder joint, and an inch in thickness, and gives 
off, about thirteen inches above its insertion, a branch to be inserted 
at the anterior border of the sternum, or breast-bone. This branch, 
which could not be well shown in the drawing, is known to anatomists 
as the cuticularis colli. There does not appear to be any occasion to 
consider it a distinct muscle ; its fibres are interwoven with those of 
the muscle under consideration ; its function is to aid that muscle, 
and fix it in its position over the shoulder joint. Though so thin, 
the weight of the mastoido humeralis is not less than five pounds. 
To give effect to this muscle,- it is necessary that its base, the head, 
should be fixed. This is effected by the complexus, and its allies of 

' This relation is not well shown in the drawings, owing to displacement, caused by the 
cord used in suspending the subject ; the artist drew the parts as he saw them, and the 
inaccuracy was overlooked until too late to be corrected. 


the neck. From this it follows that the horse, in speeding, should be 
allowed to follow its instinct in fixing the position of the head. The 
ally of this muscle is the superficial pectoral, which has its insertion 
on the anterior extremity and lower margin of the sternum, or breast- 
bone. The course of its fibres is backward, downward, and outward ; 
they divide into two branches : one is inserted into the anterior ridge 
of the humerus, along with the mastoido humeralis ; the other is 
spread out on the fascia of the inner face of the leg. The action of 
this muscle is to carry the whole limb forward, in common with the 
last described, and at the same time to adduct it to counteract the 
abduction of that muscle. 

The action of these two sets of muscles is so unlike any other that 
it is not readily understood. Let us suppose a man propelling a boat 
through the water by means of an oar, and the handle end of the oar 
made fast to the side of the boat opposite to that on which he is 
seated, but free to move about a pin ; then let the man remove the 
rowlock from its place and substitute for it his hands ; next make fast 
the blade of the oar in the water, and the man shall then apply his 
strength to the oar : the boat will move. Now, if this illustration be 
modified so that the oar shall be vertical, and the blade of the oar be fixed 
to the bottom, and the handle to a fixture above the man's head, the 
similitude will be complete. Of course the nearer the power is applied 
to the foot, or fulcrum, the faster the upper end will move, but the 
greater must be the expenditure of power. There is another muscle, 
acting from without upon the shoulder, whose office has been doubtful, 
the small pectoral. It arises from the keel of the sternum, or breast- 
bone, and passing between the shoulder and the neck, fills the angular 
space in front of the scapula. It is thick below, where it is turned over 
the breast, and becomes smaller as it is reflected on the scapula, tri- 
angular in form, to fit the space it fills, and is the muscle against which 
the collar rests ; this is a muscle of considerable power, being two and 
a half pounds in weight. It is attached to the muscles of the scapula 
by strong cellular tissue, and to the strong aponeurosis that covers it. 
Besides being an element of beauty, by giving graceful contour to the 
parts, it seems to have no other function than to pull forward the whole 


limb, rendering tense the tissues connecting it with the trunk, and by 
so doing extending the limb to enable it to take the ground farther in 
advance, and leads us to infer how great importance was attached by 
the Master Mechanic to utilizing every available means to enable the 
fore foot to reach the ground as far in advance as possible, that no 
time might be lost in giving support to the centre of gravity. 

We have thus far considered the anterior extremity as a passive 
tool taken as a unit ; it remains to study it as an active automatic 
machine. It is difficult to trace any analogy between the mechan- 
ism of the anterior and posterior extremities thus far; but in the 
system of levers, by the closing of which the limb is shortened, and 
in the opening of which it is lengthened, we recognize the same 
mechanical combinations that are employed for the same purpose in 
the posterior extremity. 

In Plate IV. the external view of the shoulder and arm is given 
showing its relation to the trunk and that of the muscles to each other. 
The pearly-colored upper border of the scapula, n, n, is seen with 
the levator anguli scapulae still attached. This border, which is car- 
tilaginous, is not seen in the prepared skeleton, but a rough margin 
to the bone indicates its former connection. No muscle of the ante- 
rior extremity, as an automatic machine, is attached to this cartilagi- 
nous border. It has not sufficient firmness to resist force from below, 
but its tenacity is sufficient to withstand great traction, and its flexi- 
bility is such as to prevent any danger of fracture by force so applied. 
The spine of the scapula may be traced from the cartilage downward, 
near the middle of it, to which the trapezius and branch of the yellow 
cord were attached. This spine divides unequally the scapula ; in front 
of it is the superspinatus muscle, s s, whose terminal tendons pass 
over the head of the humerus, or shoulder, one to be inserted into the 
external tubercle on the outside, and one third of the distance from 
the point of the shoulder to the elbow. This is the most consider- 
able division, and acts to extend the humerus on the scapula and 
rotate it outward. The other tendon is inserted near the internal 
tuberosity; it unites with its fellow in extending the humerus. Con- 
sidering this muscle mechanically, it would be proper to regard its 


lower insertions as one, overlaying the joint beneath the mastoido 
humeralis, and acting on the head of the humerus as a direct extensor 
of the humerus ; its weight is two pounds, and its length seventeen 

The shoulder joint is constructed on the same principle as that 
of the hip, but the head of the humerus is broader and less convex, 
and the cavity of the opposing articular surface of the scapula too 
small to lodge it; but it is supplemented by cartilage and ligaments, 
and held still more strongly in its position by the powerful tendons 
which envelop it. The head of the humerus is held in its place 
by the further assistance of the atmospheric pressure equal to one 
hundred pounds. Though freedom of motion is not so great as in the 
corresponding articulation in man, it is much greater than that of 
the hip joint. 

The two muscles that especially guard the joint and prevent later 
displacement are : the infraspinatus (i s), which is attached to the ex- 
ternal surface of the scapula, and nearly fills the space below its spine. 
It is inserted into the head of the humerus, at <?, directly opposite the 
shoulder joint; the other is the subscapularis ( Plate XL, /), having 
its attachment on the inner surface of the scapula, and occupying the 
whole face of the bone below the insertion of the serratus, s, and 
is inserted into the inner side of the head of the humerus, directl) 
opposite to the insertion of the infraspinatus. These two muscles 
are of the same power, each weighing two and a half pounds, and of 
the same length. Acting simultaneously, they neither flex nor extend 
the humerus, the abduction of the one cancelling the adduction of 
the other, but they are powerful braces to the joint. 

There is another pair of muscles, whose functions cannot be under- 
stood unless considered together. If the reader will refer to any one 
of the silhouettes of the trotting horse, and watch the action of the 
fore leg from the time that the foot leaves the ground until it takes a 
new position in advance, he will perceive that all the joints are flexed 
rapidly before the foot passes the perpendicular. The flexion at the 
shoulder is performed by these two muscles. One is called, by Chauveau, 
the long adductor ; teres minor, by Percivall ; and the scapula hume- 


ralis, by Legh. The other is called the adductor of the arm, by 
Chauveau ; (ors major, by Percivall ; and the great scapula humeralis, 
by Legh. One acts on the outer and the other on the inner aspect of 
the humerus, at equal distances from the shoulder joint, and nearly one 
third of the distance from the articulation ; one from the outer, and the 
other from the inner surface of the scapula; and the weight of each is 
one pound, while their length is the same. They cannot be conceived 
as acting independently of each other, and it is useless to consider 
what their function would be when so acting. Conjointly they are 
neither adductors nor abductors, but flexors of the shoulder. While 
the bone is thus flexed, the limb is brought forward by the mastoido 
humeralis, which is inserted into the same ridge as the external of 
these two muscles. 

When the time comes for a thorough revision of the names of the 
muscles of the horse (and that time must come soon, for it is now con- 
fusion worse confounded), it is to be hoped they will be determined by 
their mechanical action without reference to the action of corresponding 
muscles in man. The camera has now made the task comparatively 
easy. When that time comes, these muscles should be known as the 
flexors of the shoulder, internal and external. 

There are two flexors of the forearm. The flexor brachii is a short 
tendinous muscle, originating from the lower anterior extremity of the 
scapula, just above the centre of the shoulder joint, by a strong tendon, 
which is developed into a patella-formed cartilage, moulded to the 
double groove on the anterior angle of the humerus, over which it 
glides as a synovial articulation, or a pulley, in the same manner as the 
patella of the stifle joint, the grooves being deep so as to prevent 
lateral displacement in extreme flexion. Below the shoulder it forms 
a cylindrical muscle ten inches long. Its muscular fibres are inter- 
mingled with tendinous bands, by which its elongation is limited, and 
it is enabled to act as a ligament to support the weight of the body 
without fatigue.* It is inserted into the capsular ligament of the 
elbow joint, and the rough tuberosity at the head of the radius. It 
raises the forearm, and is one of the muscles on which, in part, the high 

See description of serratus muscle, page 62. 



action of the knee depends. The other is the humeralis externus of 
Percivall. It originates behind and below the head of the humerus, 
and, winding around that bone, fills the furrow of torsion (Plate II., 34). 
It is inserted into the anterior heads of the radius and ulna, and acts 
as an assistant to the flexor brachii : the two muscles originate from 
opposite sides, but act as a unit lifting the forearm. It has greater 
power than its associate, being larger and more muscular, and from 
its spiral course its fibres are longer ; it is capable, therefore, of giving 
higher action than its' associate. 

The triceps of the arm is a powerful muscle which plays a very 
important part in the mechanism of the anterior extremity. As its 
name implies, it is a three-headed muscle, if we choose to consider it 
one muscle, and it is an extensor; but the correspondence in name 
with the triceps extensor of the thigh should not lead us to confound 
its mechanism with that of the latter. The triceps of the arm 
(Plate IV., K) fills the angular space between the point of the elbow 
(olecranon process) and the lower border of the scapula. The infra- 
spinatus, i s, covers the origins of the three heads, but their com- 
mon insertion at the short end of the ulna, as their lever, is clearly 
shown in a strong tendon. The two upper heads are attached to the 
lower border of the scapula, and when these divisions contract they 
tend to close the angle between these bones ; but the third, or lower 
head, is not attached to the scapula, but to the posterior face of the 
humerus. This branch, sometimes called the short extensor, being 
independent of the scapula, may act in extending the arm when the 
angle formed by the latter bone and the humerus is so small that 
the limit of contraction of the other two branches is reached, as is the 
case in every instance before the fore foot leaves the ground in run- 
ning. The triceps is a powerful combination of muscles. Its length, 
varies with the distance from the joint at the shoulder, being seven- 
teen inches at its greatest and eight at the least distance. Its weight 
which is eight pounds, does not give a full conception of its power, 
for its action is nearly direct. 

The anconeus is a small muscle attached to the capsular ligament 
of the elbow joint, and is inserted into the olecranon process of the 


ulna, or point of the elbow. It contracts synchronously with the 
triceps, and its action is upon the capsular ligament to pull it out 
of the way and prevent its being pinched in the elbow joint as it 
becomes relaxed in the extension of the forearm. 

The muscles of the forearm are, like those of the posterior ex- 
tremity, simple and direct in their action in extending and flexing 
their levers, and, like those of the foot, their functions have been 
well studied and are well known. But the complex forces are the 
more difficult to understand the nearer we approach their sources, 
and have led to great diversity of opinion ; the manner in which a 
movement was produced could not be explained for the reason that 
the motion itself was not understood. Now that the camera has ren- 
dered those motions easy of analysis, it is not difficult to show how 
they are produced. 

The corresponding angles being reversed, the anatomical relations 
of the great flexors of the feet are changed. In the posterior limbs 
their tendons passed over the angles of the hock to be inserted into 
the bones of the feet. In the anterior extremities the corresponding 
tendons are enclosed in a sheath of the strongest possible construc- 
tion, into the outer wall of which the pisiform bone is placed, to afford 
better protection to the tendons in the flexions of the knee joint, which 
is double, so that when the flexion of one is completed it is continued 
in the other, and greater flexion of the metacarpus upon the radius 
is effected than would be possible were the joint single. It will be 
noticed, on reference to the silhouettes, that the knee is never bent 
when the corresponding foot is on the ground. It plays its part in the 
role of a crutch consistently, but it performs a lively part in another 
character when relieved from the weight of that responsibility. 

The tendons of the perforatus and perforans are utilized as liga- 
ments as in the posterior extremities, but with some variations rendered 
necessary by the different conditions. From the posterior surface of the 
metacarpus, or cannon bone, below the knee, a ligament is thrown out 
to the perforans tendon to reinforce it, and other ligaments or tendinous 
connections are made to prevent extension of the joints beyond that 
of the standing position, by which the tension is taken from the flexor 

7 6 


muscles, and their tendons act as ligaments, their size being out of 
all proportion to their use as tendons ; and in the extreme extension 
of the pastern the strain comes upon both tendons and the suspensory 
ligament, and extension beyond that in the standing position is effected 
only by the weight of the body, and at the expense of the elasticity of 
all combined. While rupture of these tendons is of rare occurrence 
under the strain thus put upon them, the sheaths through which they 
glide above the pastern are not unfrequently torn transversely, giving 
rise to inflammation and adhesions. 

It is stated as a general proposition that the tendons are inexten- 
sible. This statement requires qualification. That they are so under 
all ordinary uses as tendons must be admitted, but when they are serv- 
ing as ligaments, in concert with the suspensory ligaments, they are 
put upon a strain that muscle is incapable of applying or resisting. It 
is therefore, as we have elsewhere shown, that powerful branches are 
attached to the cannon bone to relieve the muscle of a strain it is not 
capable of resisting. The organic tissue is tendon, but its use in exten- 
sion of the foot beyond a certain point is that of a ligament to limit 
extension ; but as a ligament it does not absolutely arrest extension, 
for it is elastic and allows of further extension after it is put upon the 
stretch ; or the extreme extension that takes place in the fetlock, to 
allow the pastern to take a horizontal position, would not be pos- 
sible. Further proof of this will be given after a quotation from Mr. 
Percivall, which I shall give in extcnso, for the reason that the informa- 
tion conveyed by it is very important, and few in America will have an 
opportunity to consult his works, from their extreme rarity. 

" The parts sprained are naturally supposed to be ' the sinews.' But 
sinews or tendons, being both inelastic and (per physical force) inexten- 
sible, they themselves can neither be stretched nor strained so long as 
they maintain their cohesion of substance. To discover, therefore, in 
what part the sprain or lesion is likely to be situate, it will be advisable 
to submit the leg in its normal state to anatomical examination. 

" If we strip or dissect off the skin from the flexor tendons, \ve find 
underneath, between them and the skin, a quantity of loose cellular 
tissue, cutting away which we come to a close, or proper, tunic of the 


same substance immediately enveloping the tendons. This under, or 
proper, covering, however, is fibrous as well as cellular in composi- 
tion. For the space of a hand's breadth below the knee the glistening 
(tendinous) fibres may be seen crossing obliquely over the tendons, as 
they run from the annular ligament of the knee to be implanted 
into the external border of the cannon bone behind the external 
splint bone. This forms the sheath of the tendons. And when we 
slit it open we discover a cavity possessing a surface of a synovial 
nature ; and a sac, or dursa, thereby formed, which extends half-way 
down the leg, and is then closed. Through the bursa runs the per- 
forans tendon, which may indeed be said to form a posterior boundary 
to it. The interval between the flexor tendons and the suspensory 
ligament, in their front, is likewise filled with interuniting cellular sub- 
stance. This brief and imperfect anatomical sketch may serve to illus- 
trate the nature of sprain. It will at once strike us that, although 
the tendons themselves are incapable of extension, and are too firm 
ind strong in their texture to sustain hurt from any common accident, 

that they are surrounded and connected together, as well as to the 
aarts contiguous to them, by a soft, delicate tissue which must, every 
ime they are forcibly pulled or stretched, be extremely liable to stretch 
and lacerate ; and this, in fact, it is which in all ordinary cases consti- 
tutes the true and sole nature of ' sprain of the back sinews.' " 

What is proved from the facts presented in the above quotation 
is that laceration of the sheath of the tendons could not take place ex- 
cept by the elongation of the tendon itself, and on that elasticity, or 
spring, of these tendons, in conjunction with that of the suspensory 
ligament proper, the mechanical action depends and in it their chief 
value consists. 

The action of the anterior extremity as a unit in locomotion may 
now be studied. As the limb is thrown forward and in the act of 
taking the ground, it forms a straight line from the elbow to the heel ; 
the toe is raised, as in the posterior extremity, and contact is made 
with the heel. When the weight comes upon the foot the suspensory 
ligament is put upon the stretch by the reflexion of the pastern. The 
knee is kept in a straight position by the tension of the extensors, 

7 8 


while the impulse is transmitted to the humerus at the angle of the 
elbow, too rapid flexion at that joint being prevented by the force of 
the triceps at the point of the elbow and the contraction of the great 
pectoral, which, acting on the shoulder, prevents the sudden flexion of 
that joint, at the same time that it forces the body over the limb ; in 
which action it holds an analogous relation to the vastus of the pos- 
terior extremity, the application of mechanical power being utterly dis- 
similar, but the result in locomotion the same. The great dorsal aids in 
this office, though less efficiently. The superspinatus, acting from the 
scapula upon the upper end of the humerus over the shoulder joint, per- 
forms the same function for that joint, preventing its flexion too rapidly. 
The traction of the triceps upon the scapula is so great that it would 
be torn away from its position but for the counter action of the trachelo 
subscapularis, which transmits it to the cervical vertebra, as already ex- 
plained. In this order the angles at the shoulder and elbow close while 
the fetlock joint is bent until the pastern is horizontal with the ground. 
In this action the limb is practically shortened, until from the position 
of the hypothenuse it becomes the perpendicular of a right-angled 
triangle, and during this change of position it has given uniform 
support to the centre of gravity without deviation of the direct line of 
its motion. During this time the levator anguli scapulas has been 
contributing its force by acting on the short end of the lever, drawing 
it forward and adjusting the axis of the limb to its changing require- 
ments. The passing of the body over the limb in a position perpen- 
dicular to the ground enables the limb in its character as an automaton 
to exert a propelling force as well as a sustaining one. It is necessary, 
however, that the support should be constant, as before; the angles must 
open as gradually as they had closed, and the fetlock joint must be as 
gradually straightened. Some changes take place in the action of the 
forces. The superspinatus, that had been yielding to allow of flexion, 
now contracts with greater force, and its labor is rendered easy by the 
continued traction of the two great propellers acting from the thorax. 
The branches of the triceps acting from the scapula relax altogether ; 
that from the humerus by its continued contraction extends the fore- 
arm upon the humerus. This order continues to the close of the first 


half of the stride, when it is in the power of the animal to give an 
impulse to the movement, that settles effectually the question of the 
power of the anterior extremity as a propeller. The proof will be 
given hereafter, but the modus operand! is as follows: As the foot 
is about to leave the ground, the angles of the limb being extended to 
their utmost, the great pectoral, the great dorsal, and the great serratus, 
by a vigorous and simultaneous effort, in conjunction with the spring 
of the suspensory ligament and its reinforcing tendons, are capable of 
deflecting the centre of gravity of the whole body of the horse, going 
with a velocity of twenty miles an hour, four inches in a distance 
of ten feet ! 

At the completion of the stride, the last impulse given by the 
reaction of the suspensory ligament is like the spring of a bow, and 
the flexor muscles regain control of their tendons, which had just been 
serving as reinforcements to the suspensory ligament. 

At this moment, the foot being off the ground, the knee bends 
under the contraction of the perforatus and perforans muscles. The 
niperspinatus and all the muscles of the triceps are relaxed ; the 
flexors of the shoulder and of the arm contract ; at the same time the 
mastoido humeralis and superficial pectoral, acting on the shoulder, 
carry the whole limb forward on its centre, the great pectoral and 
great dorsal consenting. In this order they pass the perpendicular, 
when the order is quickly reversed ; in twice the speed used in the 
retrograde movement, the foot is again in position to take the ground. 
The extensors of the feet, after a rest of three fourths of a stride, again 
straighten the knee, raise the toe, and the triceps is ready with all its 
heads to take the shock. The sterno prescapularis pulls the slack out 
of all the tissues connecting the shoulder with the trunk, that nothing 
may be lost to effect the last line in extension. 

The action of the anterior extremity in the three characters whose 
parts it performs at the same time, we have endeavored to represent. In 
these three characters it is a complicated machine. The object in its 
construction was to enable the limb to support the body for the 
greatest length of time, and to graduate that support so that it should 
be uniform and constant, and that there should be no loss of momen- 



turn or waste of power by correcting deflection of the line in which it 
is intended the body shall move. This rendered necessary the use of 
the legs alternately, so that while one should be performing these 
functions the other should be moving in the reverse direction, to take 
its place and permit as little loss of time as possible between the end 
of the performance of one limb and the beginning of that of the next. 

If we have comprehended the movements of a limb and the relative 
value of the forces that produce them, the levers on which they act 
and the relation of the limbs to each other, we ought to be able to 
determine the mechanical elements of the qualities desired in a horse. 
If speed is desired we must look for those mechanical conformations 
of parts that determine speed, but this speed must be attained at the 
expense of power. The anterior limbs must conform in their mechan- 
ical force to the posterior, and vice versa. It was observed of the pos- 
terior limbs that long full propellers (the vasti and glutei), low hip joint 
set well back, so as to afford room for long femur and tibia, gave great 
length of limb when extended, enabling it to support the weight of the 
body and exert its propulsion for a longer time, at the same time the 
power was more directly applied when the head of the bone was lower 
down. So far as these principles can be applied to the anterior limbs 
they hold true of them as of the posterior extremities. 

It was observed by Bishop that all animals distinguished for great 
speed have the angles of the bones most inclined to one another. But 
while this mechanical arrangement gives great advantage for speed it 
is a source of weakness in bearing burdens and hauling. 

The requirements for the anterior extremities, to be in harmony 
with the posterior ones, would be a long oblique scapula and long 
humerus : these bones long, the angle formed by them would neces- 
sarily be less obtuse. The great pectoral and great dorsal are the 
muscles that hold the mechanical relation to the anterior extremity 
that the great gluteus and vastus do to the posterior; and to give equal 
advantage to them the thorax should be long to give sufficient distance 
between the ribs of origin and the insertion at the shoulder. 

The application of propulsion to the anterior limb is unlike that to 
the posterior, and as it is an advantage in the latter to have the heads 


of the femurs low down to push more directly, in the former, on the 
contrary, the centre of motion corresponding to the head of the 
femur is not at the shoulder, but as high under the withers as pos- 
sible, and the application of the propulsion as low as possible, as 
was shown when describing the action of the great pectoral ; for, 
the foot being the fixed point, the nearer the power is applied to it 
the greater will be the velocity of the upper end of the extremity 
acting as a crutch. 

In the extreme of flexion and extension, as represented in leaping, 
the muscles act at great disadvantage, as is illustrated by the difficulty 
and slowness with which an animal rises from a recumbent posture. 
They are positions incompatible with speed. 

Whether the muscles act with the greatest energy at the earlier or 
later stage" of contraction has not been determined with certainty as 
far as I know. There is no doubt, however, that they act with the 
greatest promptitude in response to the will when the limbs are 
.-lightly flexed. Boxers will instinctively put themselves in that po- 
sition when in attitude for offence or defence. Boys when about 
to start for a race will relax their extensors to get a good send-off, and 
they do not fully extend them again until the trial of speed is over. 
So the horse in fast trotting "settles to his work," as it is technically 
called. In this expression it is intended to represent the idea that 
the centres of motion are nearer the ground in order that the muscles 
shall act to the best advantage, and that in propulsion the act shall be 
most direct and longer sustained ; or, in other words, the points of 
action and reaction are in a line forming a more acute angle with 
the ground. 

M. Weber asserted that the velocity in walking will be greater the 
nearer the head of the femur is to the ground ; as this height in- 
creases the velocity decreases. One sometimes arrives at a truth by 
a very devious route, though he may have lost himself on the way. 
He proved his position by the pendulum, which has been made to 
demonstrate many a knotty proposition ; but while the leg of his 
physical horse has swung three feet, our living horse has gone forty, 
and his extremities have performed two complete revolutions. The 



speed of the horse does not depend upon the length of the limbs 
acting as pendulums, but upon the length and thickness of the 
locomotor muscles, the angles and lengths of the bony levers on 
which they act, the freedom of their articular ligaments, the corre- 
lation of all the mechanical parts, and much also on the nervous 
energy or will transmitted to the muscles, technically known as 



THE attraction of gravity, or that force which is constantly drawing 
all bodies toward the centre of the earth, is a phenomenon so familiar 
to us that we fail to realize it at all times, and the consequences that 
would ensue were it to be for one moment suspended. Like the air 
we breathe, it is one of the necessary conditions of our existence, and 
the force with which it acts on all bodies is exactly measured by their 
weight; but this is the measure of that force in bodies in a state of 
rest or inertia. The instant that support is removed and the body 
yields to that force, there enters another element that must be taken 
into account, and that is momentum. While gravity is a constant 
quantity under similar conditions, momentum is a constantly varying 

By yielding to the force of gravity an object does not escape from 
its power, neither is it reduced one grain in its influence at whatever 
rate the body falls. It is therefore an increasing quantity in a rapid 
ratio.* It is this force, which is constant and measured by the weight 

* The formula for the determination of the distance which a body will fall in any given 
time is, D = J g f in which D = distance ; g, acceleration of gravity, or 32 feet ; /, time 
in seconds. From this we learn that the distance which a body unsupported would fall in the 
first \ second would be 4 feet ; in the first \ second, 7.68 inches ; in the first J second, 3 inches. 


of the horse, that renders necessary the great development of the loco- 
motive organs and columns of support. The power of resistance of 
these organs must be equal to the attraction of gravity and counteract 
it, and at the same time be in such excess as will afford .the means of 
propulsion in a horizontal direction. The influence of gravity is not 
affected by motion in the body subject to it, at whatever rate it may 
be moving. It may be projected into the air by a force greater than 
that of gravity, but it does not escape from it in any degree. The 
force that projected it was stronger than that of gravity at the time of 
the impulse ; but the resistance of the air and the constant force of grav- 
ity would soon bring the motion to an end without the continuation 
of that projectile force. 

It is the result of this continuation of force in such directions as will 
resist the attraction of gravity, and overcome resistance to a movement 
in a horizontal direction, that we call locomotion. 

There is another physical law to the effect that a body put in mo- 
tion will continue in motion in the given direction until diverted by 
another force from another direction. The force with which a body 
moves above the surface of the ground is determined by multiplying 
its weight by its velocity, and is called its momentum ; therefore the 
force of gravity, represented by the weight, being constant in the same 
body, the momentum will be as the velocity. If the body be repre- 
sented by an iron ball weighing one thousand pounds, moving at the 
rate of twenty-five miles an hour in a horizontal direction, it will 
represent the momentum of a horse of equal weight at full speed. 
To arrest it suddenly would be its destruction. 

To continue its motion without diminution of velocity requires a 
continuous application of force, and the greater the velocity the greater 
is the necessity that the trajectory or line of motion should suffer no 
deflection, for the force necessary to correct it increases with the 

From what has been said it follows that the only muscular power 
required to keep a body in motion, at whatever speed, is that which is 
necessary to resist the attraction of gravity and overcome resistance. 
It is plain that, in order to maintain a uniform support of gravity, and 


a continuous impulse in the direction of motion, the limbs must move, 
at whatever pace, in such manner as best to attain that end; that the 
more rapid the motion, the more uniform must be the support. 

If the time occupied by a racing horse in going a mile be one 
minute and forty seconds, and the length of stride twenty-five feet, 
as represented of some horses, it would follow that he must be off the 
ground a full half-second at each bound, and according to the law of 
falling bodies he would, if he moved horizontally, during that time fall 
a distance of four feet. But in the gallop he is supposed to be moving 
by a succession of bounds in which he rises as far as he falls. This 
would give one fourth of a second as the time of descent equal to one 
foot of vertical fall to twelve and a half feet movement in a horizon- 
tal direction, and a consequent deflection of the centre of gravity to 
that extent. 

We can imagine the effect that would be produced upon a railway 
car of any description if, when going at the same rate, it should pass 
over an obstruction that would produce such a deflection of the line of 
motion ; and if instead of the railway car we substitute the horse, what 
but a broken neck could be expected ? There is no suspensory lig- 
ament, or back tendon, or joint of the body that could be submitted to 
such a shock in a state of tension, and not go through bankruptcy 

It is this deflection in the line of motion that constitutes the great 
obstacle to be overcome in all methods of locomotion. It is that 
which retards the progress of a ship in a rough sea; a certain amount 
of momentum is lost in every undulation, and power is spent in lifting 
the ship against the force of gravity that might in a smooth sea be 
spent in accelerating velocity. But a ship is an inanimate object 
acted upon by inanimate forces, and though speed is sacrificed, there 
is no exhaustion from waste of strength, as is sustained by all living 
beings in contending against the law of gravity, which requires a 
greater expenditure of force to arrest a body in its fall than is required 
to sustain it in a state of rest. 

The most perfect method of quadrupedal locomotion, therefore, is 
that in which the greatest speed is attained with the least expenditure 
of vital force. This is found in those quadrupeds in which the devia- 



tion of the line of motion from the horizontal is least. Pre-eminent 
among these are the horse and hound, whose mode of progression is 
the same. Though the deer and hare may have the advantage for 
a short run, yet the method of progression by bounds, used by these 
animals, sooner fatigues them, and in a fair field they will be run down 
by the former from sheer exhaustion. To this subject we shall refer 
again when we analyze the paces of the deer and dog. 

In the two preceding chapters we have condensed the anatomy of 
the locomotive organs into as small a space as possible, and at the 
same time have, with the aid of accurate drawings, endeavored to 
make the mechanical action of all the limbs individually so intelligible 
that any one of ordinary information may comprehend them. We will 
now proceed to show how these forces are co-ordinated in the produc- 
tion of the different paces when all the limbs are in action. Instead 
of the mingled confusion of limbs and display of brute force, one may 
see the most perfect order and regularity. In the slow movements 
the limbs of the horse are without doubt much under the control of 
the will ; he may use his anterior ones to strike, paw the ground, and 
in various ways show the control he has of different muscles in the 
performance of their various functions ; he may rear and kick, toss his 
head and lower it to the ground, as in drinking, grazing, or sauntering; 
but when speeding, whether from ambition or terror, all this trifling is 
laid aside, the position of the head becomes fixed as a base of action 
for the muscles of the neck and head, the detailed action of the va- 
rious parts of the animal are lost in the complicated machine, and 
the whole acts automatically, as the movements of the various parts 
of a locomotive are lost in the combined action of the engine to 
which they are subordinate. 

The run is the perfect gait of the horse, for it is that which displays 
most perfectly the play of all his locomotive organs, by which he at- 
tains his greatest speed, and to which he owes his preservation in the 
long struggle for existence through which he must have passed before 
he came under the protecting care of man. It is the gait, therefore, 
which best serves as a subject to study the law, or the theory of his 
locomotion. To any one who has followed the anatomical analysis 


of the last t\vo chapters, the theory may have already outlined itself; 
but it is desirable that it should be made clear to all, and many of the 
anatomical facts demonstrated in the last chapters must be taken for 
granted in this by those who have not given the necessary attention 
to the anatomical descriptions. Perfect quadrupedal locomotion re- 
quires uniform support to the centre of gravity and continuous pro- 
pulsion by each extremity in turn. 

In order to avoid the abstract study of the co-ordination of the 
limbs in locomotion, figures are given to aid the mind in following the 
movements. They were executed by a process called photo-engraving, 
after drawings made with great care from a series of photographs, and 
represent twelve views of as many positions of a running horse. Three 
horizontal lines are drawn above the base at intervals of one hand, or 
four inches, as a guide to the eye in determining the elevation of the 
feet, and a fourth near tlvj back to show the deviation from a horizontal 
line of the centre of gravity, which we will suppose to be under the 
saddle. These cuts are not introduced for their accuracy ; they have 
been subjected to too much manipulation to lay claim to that precision 
of outline that will be found in the heliotypes and silhouettes in photo- 
lithography given in illustration of the paces. 

FIG. i. 

Fig. i. gives the position of the animal in readiness to start, 
height is a little in excess of sixteen hands. 




We have inserted two plates of the skeleton in the positions corre- 
sponding with Figs. 6 and 1 2 in order to enable the reader to under- 
stand their action in the various movements, and by reference to Plate 
II. he will be enabled to follow the descriptions in this chapter, and 
the action of the various muscles that produce them, as described in 
the previous chapters. 

FIG. 2. 

Fig. 2 represents the left fore foot upon the ground nearly under 
the centre of gravity; the centre of motion for the corresponding limb 
has passed in advance of the foot, and a line drawn through these two 
points would not be perpendicular to the surface of the ground ; or, for 
brevity of expression, we will say he has passed the perpendicular. 
The limb is being elongated or extended by the straightening of the 
pastern joint and the joints at the elbow and shoulder ; by these means 
the support given by the muscles is continued. In this position there 
is no muscular force exerted upon this limb below the knee. It was 
shown at page 76 how the " back tendons," while the limb is in this 
position, are converted into ligaments over which their muscles have 
for the instant surrendered control, and in conjunction with the suspen- 
sory ligament are supporting the weight of the body by their passive 
resistance. As the body advances by its own momentum and the con- 
tinual action of the great pectoral and dorsal muscles, the pastern joint 


becomes nearly straight, and the pastern bone resumes its position 
under the metacarpus, or cannon bone, and while that joint is still 
supported at its convex posterior surface by these powerful ligaments ; 
and as the limit of extension is reached and the limb is at an angle 
with the ground of forty-five degrees, a vigorous concerted action of the 
propellers sends it forward and upward in the direction of the axis of 
the limb with a force so great as to close the space between the croup 
and the gauge line above it, and all his feet are in the air. If this force 
had been applied, as is popularly supposed, by the posterior extremity 
and behind the centre of gravity, the result would inevitably have been 
to pitch the animal headlong to the ground. The position of the fore 
leg just before it leaves the ground is best shown in Fig. 12. 

FIG. 3. 

Fig. 3 shows the feet all in the air. The foot which rested last 
upon the ground is now eleven inches above it and moving rapidly 
to the front. The interval of time between the photograph of the 
horse in position No. 2 and that of No. 3 was greater than that which 
passed between No. 3 and No. 4, owing to want of uniformity in the 
tension of the threads making the magnetic circuit. This defect was 
subsequently remedied ; and in the series of views illustrating the run, 
in which the gait was more thoroughly analyzed by a larger number 
of cameras, the intervals are very regular. 

9 o 


FIG. 4. 

In No. 4 the upward impulse given by the fore leg may be supposed 
to have reached its limit, the croup having passed above the gauge- 
line marking the elevation, and the feet are all gathered under the 
trunk more than a foot above the ground. There is now an oppor- 
tunity for the animal to change their order ; for, as has been stated, 
he cannot change the order of his feet when one of them is on the 
ground, and he is going at a rapid rate, without subjecting himself to 
a fall. Although the distance passed over from the time the last foot 
left the ground until the next one reaches it is only equal to the 
interval of any of the feet, and the time that has elapsed while this 
has been taking place does not exceed perhaps a fifth part of a 
second, still it is sufficient to enable the animal to choose whether 
he shall lead with one foot or the other in the next stride. But the 
time, short as it is, is sufficient to cause a descent of four inches, and 
the momentum acquired makes the contact with the earth a much 
more serious matter than in any other portion of the stride. To make 
it with either of the anterior extremities, or both, as is popularly be- 
lieved to be the case, would seriously check the momentum, if it did 
not result disastrously to the unlucky member. But this has been 
shown over and over, by numerous observations at Palo Alto, never to 
take place in running. The first check to the descent of the centre 


of gravity is given by one of the hind legs, and by that one which 
is diagonal to the fore leg leaving the ground 'last; but, to reach 
it in such manner as to prevent a catastrophe, it must be planted 
beneath the centre of gravity or in advance of it, and then, in order 
to prevent the anterior part of the body from falling forward, it is 
necessary that all the available force should be brought to bear 
upon the right hind leg as a lever with its fixed point upon the 
ground. How this is effected, and by what muscles, is shown at 
page 58. 


This situation is shown at Fig. 5. The picture was taken almost at 
the instant of contact by the right hind foot with the ground. The 
anterior portion of the body is arrested in its downward course, not 
by its own limbs, but by the contraction of all the muscles forming 
the external periphery of his body, from the neck to the flexors of the 
foot ; by which combination of forces the whole body forward of the 
head of the femur is not only arrested in its downward course, but 
lifted, while the momentum in a horizontal direction is maintained 
chiefly by the contraction of the vastus shortening the distance be- 
tween the lower extremity of the femur and the spines of the sacrum, 
pushing the pelvis forward from its fossa behind the head of the 
femur. The body is propelled forward with a part of the same power 
that lifts it. In this manner it does not check the momentum ac- 

9 2 


quired, as would have been the case had one of the fore legs been 
thrust forward to the ground, and the danger of stumbling is averted. 

FIG. 6. 

As progression continues, the limbs are all taking positions in the 
order they will be required to perform their functions. The right leg 
in Fig. 6 is passing the perpendicular; the pastern is bent to the 
ground to shorten the limb, and the left hind foot is descending to 
repeat the same action, when the right, from the advancing position of 
the body, will be unable to continue its support, and the right or diago- 
nal fore leg is straightening to take its turn after the left hind one. 

FIG. 7. 



In Fig. 7 the left hind foot is supporting the weight, and already the 
centre of gravity has passed over it, while the right, relieved from that 
duty, is exercising its function as a propeller, and the right fore leg 
is reaching forward to take the ground as far as possible in advance ; 
the foot is extended to bring the heel, with its elastic cushion, first in 
contact. The left fore leg is straightening to take its place in the 
order of succession. 

FIG. 8. 

The right hind leg has given its final propulsive impulse in Fig. 8, 
and the tensor vaginas femoris, the iliacus, sartorius, and superficial 
gluteus are in the act of flexing the stifle and advancing the leg to 
a new position. The left hind leg has passed the perpendicular, and is 
no longer in a position to give much aid as a supporter to the centre 
of gravity ; but the right fore foot has reached the ground, and takes 
its position as a supporter of the weight of the body, dividing the 
burden with the left hind leg still upon the ground. 

In the last chapter it was shown how the limb is thrown forward 
into this position, and how the shock of contact is transmitted, through 
the straightened extremity, to the humerus and scapula ; and unneces- 
sary flexion of the elbow and shoulder joints is prevented by the tri- 
ceps of the arm and superspinatus muscles, while it continues to give 
uniform support to the body, at the same time that it shortens by the 



gradual flexion of those joints and the bending of the fetlock as the 
body passes over its point of support. 

The danger to be apprehended in the use of the fore leg to arrest 
the downward movement when the body was falling, as in Fig. 5, does 
not exist in this position, as the momentum of gravity has been ar- 
rested by the posterior extremities, and the centre of gravity has 
reached its lowest point, while the weight is divided with the hind leg. 
Propulsion is now going on in the fore leg through the great pec- 
toral and dorsal, and in the hind leg through its propellers proper. 

FIG. 9. 

The right fore leg in Fig. 9 is now taking the entire weight of the 
body, is nearly perpendicular, is correspondingly shortened, and its 
fellow is extended forward in the position to take its turn. The left 
hind foot is clear of the ground, and the right has been elevated by the 
action of the semitendinosus slightly flexing the stifle. The settling of 
the body has not varied much from the position seen in the last figure. 
Propulsion by the great pectoral and dorsal on the fore leg, which is 
also bearing alone the full weight of the body, is most energetic, and 
to the best advantage. 

In the interval that has passed between the position of Figs. 9 anc 
10 the left fore foot has descended twelve inches, is only four inches 
from the ground, and must be considered as in the position in whicl 


FIG. 10. 

the heel makes contact with it. The right leg is elongating, and 
making propulsion by so doing, in its function as an automaton and 
also as a passive tool, by the great dorsal and pectoral making traction 
from the flanks upon the shoulder. The support it is giving to the 
weight of the body is shown by the narrowing of the space between it 
and the gauge line. This action is not yet complete. Both the hind 
feet are nearly equally elevated, but the right leg is more flexed. The 
increased flexion of the stifle renders necessary the flexion of the hock- 

FlG. II. 



joint, for, as already shown, they act together automatically. The 
flexors proper of the thigh are now making their force felt with that of 
the semitendinosus, and the stifle is being drawn forward. The flexors 
of the foot, being propelling muscles, are inactive, and the semiflexec 
position of the joints of the feet is owing to the reaction of the suspen- 
sory ligaments. 

In Fig. 1 1 the right fore foot is clear of the ground, and the left is 
in a position corresponding with that of the right in Fig. 9, but 
right is not in a corresponding position with the left in the same 
figure. The right hind foot is preparing to take its place in the order 
of succession, to be followed by the other hind foot in its turn. 

FIG. 12. 

In Fig. 1 2 the stride is completed. On comparison with Fig. 2, it 
will be seen that the body is advanced somewhat beyond that in the 
latter, and it is again about to leave the ground with the left fore foot, 
and the energy of the propelling forces have already sent the body up 
nearly to the horizontal gauge-line. This order in the movement is 
continued until the animal feels fatigue in the left fore leg from the 
continued use of it in giving the final impulse to clear the ground, 
when, as before said, it is in his power to change it and leave the 
ground with the other fore leg. 


It seems, at first thought, from the manner in which the labor is 
thrown from the leading fore foot to the diagonal hind one, during 
which the body has no support from cither, that the theory of constant 
support and continuous propulsion does not hold true, that a perfect 
machine should require no such hiatus. If the machine had been 
constructed of inorganic and inanimate material, incapable of fatigue, 
it could have been so arranged that the hiatus would not have been 
necessary; but the Creator did not, if he could, build an animate 
machine that would not tire. The animal is shown in the above 
figures as moving his feet in the same order, and, but for some ar- 
rangement that would permit of a change, fatigue would be inevitable; 
but that change would not be possible until all the feet are clear of 
the ground. If the attempt should be made while one foot is on the 
ground, the result would be called a misstep and a fall. The opportu- 
nity is afforded when the extraordinary propulsive force, given by the 
fore leg that leaves the ground last, projects the body upward, giving 
a time equal to one fifth of a stride for the hind foot of the same side 
to take the place of the one that would have followed had the same 
order continued. The coincidence of the act of changing the order of 
the feet with the exposure of the negative plate in the camera, which 
is too short a time for computation, must be very rare, and has not 
been observed in any of the many pictures taken at Palo Alto ; but 
the change is felt by the driver when the feet again take the ground, 
and it is said to have been discovered in the changed order of the 

While the run requires that each limb in turn should act as 
propeller and supporter in regular order, it cannot be executed at 
a low rate of speed, for the base of support is confined to one foot, 
and it must be rapidly adjusted to the changes of the position of the 
centre of gravity, for the same reason that a boy on stilts requires 
to be continually in motion. If the horse's speed is diminished to 
a great degree, he will change to a canter, which is a pace modified 
from the run, as may be seen by reference to Plate XXVII., or, 
what is more usual, to a trot, in which he uses two diagonal feet as 
bases of support. 



The order and action of the limbs are uniform in all the numerous 
trials of running horses photographed at Palo Alto ; so that it may b 
considered that they are in conformity with a law. Five series of th 
photographs are given, of horses representing different rates. Th 
first is that of "Mohammed," whose stride is 15 ft. 9 in.; and the 
last, that of " Florence Anderson," with a stride of 20 ft. 6 in. All of 
them were going at a moderate rate. The numbers, and correspond- 
ing lines on the ground, indicate spaces of one foot ; and as the pho- 
tographs were taken in succession at the same intervals, they will 
be understood to show the position of the limbs at each interval of 
one foot. The position of the camera is indicated by the direct line 
on the ground, and is that of the observer. In the last series the 
gauge line shows how little the centre of gravity is deflected in its 
trajectory from a direct line, and this line will be found to vary least 
when the speed is the greatest. By the aid of these lines and their 
figures the reader may be able to measure the strides and parts of 
strides, and determine their respective intervals. 

It has been observed that there is not perfect regularity in the line 
of the footprints of a running horse, especially if the ground is uneven. 
This is owing to the variations of the centre of gravity, which compel 
the corresponding variations of the positions of the small base which 
supports it ; through an instinct of the same kind which we recognize 
in ourselves, and make use of when we fail to give proper attention to 
the ground on which we are walking and govern the movements of 
our feet accordingly. This we do not always do, and the effect is to 
cause us to stagger even when we are sober. This instinct must be 
regarded as existing in a higher degree in a horse, as his locomotive 
apparatus is more complicated and of a higher order than that of man. 

If the reader is interested in knowing how far this law of the mech- 
anism of running holds, he may follow it in the succeeding plates. 
He will see the same movement in the greyhound, Plates XVIII., 
XIX., and in Plate XX. two hounds running at unequal rates of 
speed. It is the same in the ox running, Plate XXL, and has been 
proved true of the goat, and will be found to hold true of all those 
quadrupeds whose four limbs are of like proportions. 




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There is another class of quadrupeds, whose posterior extremities 
are developed to a much greater degree than the anterior ones, and 
their mode of progression varies more or less from the theory of motion 
as given in the preceding pages. The only one of this class of whose 
stride \ve are able to present an analysis is the deer. In this animal 
the same order of succession of the feet may be observed ; but, at the 
moment when it might be expected that he would, as in the horse, rise 
from one of the fore legs, owing to its feebleness he fails to do so, but 
the hind legs are thrust forward to the ground, one of them in advance 
of the fore foot and the centre of gravity, and, while one of the fore 
legs still supports the weight of the anterior part of the body, by the 
combined action of the posterior extremities he projects himself by 
a bound, and alights, not upon one of the hind feet, but upon one of 
the anterior extremities ; but the action of the limbs in pairs is not 
synchronous, one of them being a pace in advance of the other, to dis- 
tribute the shock. This mode of progression the deer is able to per- 
form by reason of the length and angles of the bones of his limbs 
and the lightness of his body, and it is adapted to the nature of the 
ground among the hills where he finds his only safety, and where 
the horse would be at as great a disadvantage as the deer is upon the 
plain. For reasons already stated, it is not possible to sustain this 
gait for a long time from the exhaustion which it produces. The 
action of the horse in leaping will be reserved for another chapter. 

From the knowledge we have gained, by the use of instantaneous 
photography, as to the action of the feet in running, the answer to the 
questions propounded by William Percivall thirty years ago is obvious: 
" What is the reason why the flexor tendons fail so much more fre- 
quently than others ? Another, Why those of the fore limb should 
fail rather than the flexor tendons of the hind leg." * 

In the following quotation he gives the answer to his own question, 
in accordance with the heretofore accepted theory of the run. " I 
have more than once had occasion to direct attention to the important 
functions performed by the hind limbs in the acts of progression, and 
to contrast these with the comparatively light duties of the fore limbs. 

Hippopathology, Vol. IV. p. 346. 


While the former, like a pair of oars at work in a boat, are plying for- 
wards and backwards, forcing the body onward, the latter, more like 
stilts, are employed in sustaining the propelling parts, lest the body fall 
forward to the ground. I have likewise afore observed, that two such 
different functions necessarily distress different parts of the limbs, 
the hock being the part most exerted in the hind, the feet and legs the 
parts most tried in the fore limbs. What distresses the sinews of the 
fore limbs so much is the extreme distension, almost preternatural, to 
which these legs are put in hard galloping and leaping every time the 
weight of the body descends upon them, at a moment when they are 
stretched out to their utmost, as they must be, to receive it ; and it is 
to this identical position of the limb, whenever any weight or force 
of extraordinary amount, or in any sudden or unexpected manner, 
descends upon it, that strain or sprain is produced." * 

It is now perfectly clear that it is in their action as propellers 
that the flexors of the fore leg become injured in their tendons, and 
in the position shown in Fig. 12; though there is little doubt that 
if the weight of the rider were not superimposed to that of the horse, 
this accident would rarely happen. Sprains involving the ligaments 
of the joints may occur at any time when the foot from any cause is 
not set squarely upon the ground, but this is an accident of quite a 
different nature from that to which reference is made above. 

We have designated the pace under consideration as the run, 
the pace used in racing, or the fastest known to the horse and other 
domestic animals. What, then, is the gallop ? If we are to be con- 
fined to the definition of the gallop given in the dictionaries, and 
generally accepted by all writers on the horse, we are forced to the 
conclusion that there is no such pace, that it is a fiction. Webster 
defines the gallop as " a mode of progression by quadrupeds, par- 
ticularly by a horse, by lifting alternately the fore feet and the hind 
feet together, in successive leaps or bounds " ; and Worcester, " to 
move forward as a horse by such leaps that the hind legs rise before 
the fore legs quite reach the ground." That the pace which we call 
the run is not such as will bear the definition given is very clear. 

* Hippopathology, Vol. IV. p. 346. 


The camera has, under the direction of Mr. Stanford, been made to 
analyze all the paces, and none has been discovered that answers to it ; 
yet it is to this pace that the term "gallop" has been always applied. 

When, three or four years ago, the results of Mr. Stanford's experi- 
ments with twelve cameras were distributed in art circles, the photo- 
graphs sent met everywhere with surprise and incredulity, and in some 
quarters with ridicule and burlesque. Such result ought to have been 
expected. They were not understood, and the revelation was so an- 
listic to all received opinions from the earliest times, that one 
could not help but laugh ; and that they do not understand them 
now does not surprise us, for hippo-anatomy has been always taught 
under the light of a false hypothesis. When we consider how little 
the simple movements of the trot were understood by the most learned 
of the teachers of animal motion, is it a matter of wonder that the 
complicated mechanism of the run had been kept so profound a secret 
in the open face of day from time immemorial ? 

A revelation so startling as that made by the camera carried results 
too far-reaching and revolutionary to be at once accepted, though it 
came direct from heaven. There is too much capital invested in 
works of art all over the civilized world to permit the innovation 
without protest, and ridicule is the cheapest argument that can be 
employed in controversy, for it does not require truth for its founda- 
tion, and but a low order of talent for its display. 

All artists know the value of the horse as a chef d'ceuv re, and he 
is made, next to the human figure, the first subject in elementary 
studies in art ; but from what source have been derived all the models 
of horses in motion ? Who does not tire in looking over the monot- 
onous repetition of outstretched legs, as if their bearers had been shot 
from a cross-bow, and were moving at a mark without any agency of 
their own, and when the slightest variation of that inflexible form 
would spoil the pose and ruin a picture. We are told that the object 
is to represent action. \Yould not that object be more readily attained 
if some position were represented that is known to be true, instead of 
one that is proved to be impossible ? " But art must represent things 
as they seem," says an objector. Those who think they see a horse in 


the positions given in the conventional way have their conceptions 
formed by a false hypothesis; those' who are initiated into the true 
theory of the movement experience no difficulty in perceiving the 
movements of the limbs in precisely the manner represented in the 
plates here given, and wonder they never saw them so before. One 
will recognize this movement more readily in a dog running than in 
a horse. 

Some of these positions seem grotesque, but for no other reason 
than because the action is not understood. When it is so, they will 
appear as necessary progressive stages in a never varying series of 
movements, the result of which is locomotion, and it will appear that 
it cannot be performed without them ; the eye that understands them 
can never be deceived, and the slightest deviation from the law of their 
co-ordination will instantly be detected in a silhouette as surely as the 
animal would be to suffer the consequences of a misstep. 

Quadrupeds will be recognized as being possessed of locomotive 
machinery, self-moving, with all the parts acting in perfect harmony, 
and not passive projectiles. If Art is the interpreter of nature, as is 
claimed, she is false to her mission when she wilfully persists in per- 
petuating a falsehood. But in this case she cannot if she would. 
Once attention is called to the true theory of quadrupedal motion, 
the truth of each one of these positions, and the interpretation of them 
in relation to progression, is so quickly recognized, while the error of 
the old theory of the gallop becomes so manifest, that artists will no 
more be able to claim that they represent nature as she seems, when 
they depict a horse in full run in the conventional manner, or the 
mythical gallop. 

Plates XXV. and XXVI. represent sketches taken from elemen- 
tary drawing-books manufactured in London and Berlin and used in 
the schools. They are heliotyped, on a reduced scale, in order that 
there shall be no suspicion of inaccuracy in the copies. 

After what has been said, comment is unnecessary ; but I would 
ask, if animal motion is to be always taught to follow such severely 
false models, wherein is it better teaching than that of the priests of 
Osiris, with whom all forms were .stereotyped for thousands of years, 





and the last stages of their art were worse than the first ? And here 
1 would diverge still farther from the path I had marked out for 
myself, to protest against the soundness of that dogma that art should 
represent things as they seem. I will not enter upon a discussion of 
the general proposition, it would carry me far beyond the special 
subject of this essay; but I will limit myself to the consideration 
of the proposition as it is applied to the representations of the move- 
ments of the limbs of the horse in motion. I am often told that 
we do not represent the spokes of a carriage -wheel in motion as dis- 
tinct spokes, but they are made to run together as they really appear 
to the eye, where new images are made upon the retina before the 
first are lost. Lightning is represented as a zigzag line, when in 
reality it is a spark ; but this spark moves with such inconceivable 
rapidity that it is quite impossible to calculate the time of its passage. 
The track of the electric spark is unquestionable, and when that is 
represented there is no untruth : it would be impossible to represent 
lightning in any other way. Lightning is not only the spark, but 
the track it describes in the sky also. To represent them thus is 
to represent the actual truth, and so it expresses action, and no error 
is inculcated. But does one ever represent the horse's legs in that 
manner to express their action ? Why not ? If it cannot be done, 
why assume a false and hackneyed position that cannot be true ? 
Why must every equestrian statue in Europe follow the model of the 
Antique Balbi in the Neapolitan Museum, with the bones of the fore 
leg flexed at right angles, and the other three feet upon the ground ? 
No such position was ever true, nor can it seem to be so to any one 
who gets his impressions from nature. 

The theory of the run and the mechanism of the locomotive 
apparatus of the horse will soon be common property among admirers 
of the animal ; and when that knowledge becomes general, all the 
famous paintings in which he is a prominent figure in the " gallop " 
will be relegated to the museums as examples of old masters, to 
illustrate the progressive stages in the development of art. 

If the theory of the run is understood, the action in the canter will 
present no difficulty ; for the theory is the same in both, and the varia- 



tions in the order of movement of the feet are changes rendered neces- 
sary by the low rate of speed in the latter. In Fig. i, Plate XXVII., the 
cantering horse is seen in the act of leaving the ground with one fore 
foot as in the run, and his feet are clear of the ground only for the dis- 
tance of two feet and five inches, as indicated by the lines on the ground, 
when the diagonal hind foot comes to the support of gravity, not under 
its centre, as in the run, but behind it (see Fig. 4), and therefore cannot 
prevent the body from falling forward. In order to prevent this result, 
it is necessary that one of the fore feet should support it, and it is 
always that fore foot which is diagonal to the hind one that is upon the 
ground. The other hind foot follows at the usual distance from its fel- 
low. He has now, through three Figures, three feet upon the ground, as 
in the walk, after which the order of the run is resumed. Fig. 1 1 nearly 
corresponds to Fig. i ; the difference observed is owing to a want of cor- 
respondence in the time of exposure of the sensitive plate of the camera. 
In Fig. i the fore leg has given its quick thrust, and the knee is slightly 
bent as it is about to leave the ground, while in Fig. 1 1 it is still acting 
as supporter and propeller. 

It is clear that if the animal moved with more will and greater speed, 
planting his hind foot farther forward in support of the centre of gravity, 
there would have been no necessity for the fore leg to have performed 
that office ; and the pace would not have differed from the run. The 
length of time during which three feet support the body gives time for 
the rider to settle in the saddle, and causes that easy cradle-motion 
which makes it a favorite gait with ladies. 




















THE leap cannot be properly considered as a pace ; although it is a 
mode of progression, it is not a continuous one. Before any quadruped 
will venture to undertake it, he must have acquired a considerable 
degree of experience in locomotion, and that confidence in the use of 
his limbs which experience only can give. That it is naturally 
acquired, there cannot be a doubt, as it is necessary to all quadrupeds 
in a wild state to enable them to overcome obstructions otherwise 
insurmountable. The weight of the horse's body, however, renders it 
necessary for him to reduce his speed, and with it his momentum, 
before he can safely attempt it, even when the obstruction is of mod- 
erate height. It is a feat in which he is excelled by most quadrupeds, 
all the quadrumana, and even by man himself. 

I'rom the mode of action of the various parts of the locomotive 
machinery, as shown in Chapters IV. and V.; the reader will experience 
little difficulty in understanding what takes place in the leap. The 
action is so full of interest that we have given a number of illustrations 
to enable the reader to observe the many different phases the leap 




presents. All the plates show the horses approaching the barrier at a 
run ; but no sooner is it observed than they begin to shorten their steps 
and apparently measure its distance. In Plate XXVIII. the hurdle is 
placed at an elevation of three feet six inches, and the horse betrays 
his anxiety by shortening his paces, and advancing with both hind feet 
nearly simultaneously and alternately with one fore foot, or what is 
called prancing, until he has approached the barrier sufficiently near 
to satisfy himself that he can surmount it, when he plants his hind feet 
well under the centre of gravity, and instantly the fore leg resting upon 
the ground gives the thrust explained in Chapter IV., by which the 
anterior portion of the body is raised, and the action is immediately 
followed by all the muscles of the haunch, which project the body to 
the required height. The anxiety and want of confidence of the 
animal are betrayed by the nearness of his approach to the obstacle 
and the arrest of his momentum before he ventures the leap. By 
the arrest of his momentum he has diminished the danger of injury 
to the back tendons on reaching the ground again. 

In Plate XXIX. we see the same horse under somewhat altered 
conditions. The hurdle is six inches lower, and he advances with 
increased confidence, leaving the ground eleven feet from it. 

The relations of the levers, or passive parts of the machine, in the act 
of leaving the ground in leaping, are shown in Plate XXXV. Fig. i, 
where the positions of the posterior extremity are the extreme of 

The next plate represents a full series of views by twenty-four cam- 
eras, by means of which the movements in leaping are carried four feet 
farther. The posterior extremities from the extreme of extension, on 
leaving the ground, pass to the opposite extreme of flexion as they pass 
the barrier, and both the posterior and anterior limbs, as they pass suc- 
cessively in pairs, are so nearly in unison that they seem in the silhou- 
ette to coincide. Plate XXXII. shows the same horse as seen in the 
last preceding plate, after he has passed the hurdle and is nearing the 
ground. The anterior extremities, that coincided in passing the hurdle, 
are now separating in order that they shall not make contact with the 
ground at the same time. One of the fore legs is extended as in the 

* fc 

J> W 





























run, to check the force of the descent, which, from the loss of hori- 
zontal momentum, has little more than the momentum of gravity to 
deal with. This is the moment of extreme clanger to the pastern joint 
and flexor tendons; but before these parts are put to the extreme test 
the other fore leg comes to the relief of its fellow, and immediately 
after the posterior extremities, one after the other, are planted under 
the centre of gravity, and by their great lifting force relieve the ante- 
rior extremities, and all the limbs are free to act their various parts in 
the run, which is not fairly resumed in this series, the velocity at 
no time being sufficient to enable the animal to clear the ground. 
The action after the leap may be still further traced in Plate XXXIII. 
where the run is not yet fully resumed, the speed being only equal to 
the disposition of the limbs as in the canter, the order being the same 
as in the run. The last illustration of the leap that we offer is very 
curious. The horse was very reluctant to perform the leap required of 
him, and came to a standstill immediately in front of the hurdle, and 
only after great urging did he attempt to surmount it. The action of 
the locomotive organs is shown to be the same in this as in the other 
series representing the leap, only with less courage manifested ; and 
there is little danger in its execution. As the horse lost his horizontal 
momentum before leaping, so he had none when he reached the ground 
on his descent. It should be observed that in all these series the 
intervals between the successive pictures are those of space and not of 
lime, as the horse makes his own pictures in a manner that will be 
fully explained in the Appendix. The intervals in all the series of 
twenty-four pictures represent distances of one foot in a horizontal 
direction. Fig. 2, Plate XXXV., shows the position of the skeleton 
as the animal meets the contact with the earth. By means of these 
skeleton views the reader is enabled to build up the entire loco- 
motive apparatus with the aid of the anatomical plates, and satisfy him- 
self as to the forces that are employed in producing the movements. 

On reference to Plates XXIII. and XXIV., it will be perceived how 
great is the correspondence in the action of the deer in bounding and 
the horse in leaping. In both the action on leaving the ground is 
the same. When the hind feet are upon the ground, well under the 


centre of gravity, the spring of one fore leg lifts the anterior half 
the body, and, the action of the posterior extremities immediately fol- 
lowing, the whole body is projected into the air; but, the deer being in 
more rapid motion, his feet take the ground at longer intervals and 
more regular order, and so diminish the danger of stumbling, as well 
as distribute the shock of contact and equalize the support of the 
weight of the body. 

When the horse reduces his speed in running so that he can no longer 
maintain his balance upon one foot, he will usually drop into a trot, which 
is a gait having two feet as bases of support instead of one. The theory 
of the trot is the same as that of the walk, but adapted to a higher rate 
of speed. It differs from a walk in that the latter has always two feet 
upon the ground, while in the trot there is always a space of time, of 
greater or less amount, in which all the feet are off the ground. Other 
differences will be noticed when we come to analyze the walk. They 
correspond in that the weight of the body is borne by the diagonal 
extremities alternately, and in the general co-relation of the limbs in 
their mechanical action. The action in the trot is the more vigorous 
as the distance in which the body moves unsupported is increased. 
The definition of the word step in its general use is somewhat 
ambiguous. It is often used synonymously with stride. In the step 
of both quadrupeds and bipeds it is understood to mean the distance 
spanned by the two feet both resting on the ground. This will vary 
with the muscular energy, but is limited by anatomical proportions. 

The stride is here used to signify the distance passed over by one 
foot from the time it leaves the ground until it reaches it again, 
measured to corresponding points, and is equal to two steps ; but in 
the trot this definition will not hold good, for there must be added a 
certain distance, differing according to speed, in which neither of the 
feet will be on the ground. If a represents the step in the walk, and 
x the distance passed over by the foot after the other foot is raised, 
the step in the trot would be expressed by a + x, and when a 
constant, the step will vary as x. In the run, there being four steps, 
and an interval when all the feet are off the ground equal to a step, 
the stride would be expressed by 5 a. The stride is divided in the 


trot into two periods by the alternate feet, so that in the trot the 
horse is twice clear of the ground in each stride. The step being sup- 

1 to be a constant quantity in the fast trot, the stride can be ex- 
tended only by increasing the space which the body passes over with 

ntre of gravity unsupported. \Yhile in the slow or jog trot this 
distance is small, in the flying trot it exceeds that in which the body is 
supported, and hence arises the great difficulty in attaining a high rate 
of speed. As was stated in the preceding chapter, the law of falling 
bodies increases the difficulty in locomotion in the ratio of the square 
of the time in which the body is so unsupported. It becomes a ques- 
tion of power of resistance, or strength of the parts on which that 

:.mce depends. On the other hand, the strength of the parts, as 
the joints, bones, ligaments, and tendons, involves increase of weight, 
which is incompatible with rapidity of movement, without a corre- 
sponding increase of power of the muscles and weight of the body to 
he borne, so that the limits of speed attainable in a trot are reached 
more rapidly than in a run, in which the limit is to be found in the 
measure of activity. 

In the run the stride is divided into five parts, instead of two, as in 
the trot, each limb taking its turn as supporter and propeller, with a 
scarcely appreciable interval between, and an interval between the last 
fore leg and the first hind one representing a fifth of the whole stride. 
Each limb, therefore, works one fifth of each stride and rests the other 
four fifths. The longest stride given of the run, in the examples fur- 
nished, is that of " Florence A." (Plate XVII ), where it is given at 
twenty feet six inches, or a little more than four feet as the portion 

;ned to each limb. It will be observed that in the trotting horse 
(Plate XXXVI.), whose stride is given at eighteen feet three inches, 
the time of support by two limbs is about the same, while the time in 
which there is no support given is greater, and divided into two inter- 
vals. So in Plate XL. the gravity is supported about half the time by 
limbs, and the other half by none, alternating every four feet. 
Notwithstanding the wonderful mechanical provision in each of the 
four limbs to secure uniform support and propulsion while the feet rest 
upon the ground, the instant that the body ceases to be supported it 


becomes subject to the law of the descent of falling bodies and all its 
consequences, as mentioned in the last chapter, and the greater the 
speed of the animal the more serious the possible consequences ; and 
though no small advantage is gained by relieving the horse of the 
weight of the rider, and placing it upon a sulky, it is the cause of 
serious damage to the finest stock. It is no small accomplishment 
in a horse, however thoroughbred, to be so well disciplined that he 
will not break from a fast trot, however goaded by his driver and his 
own ambition in a sharp contest, into a pace in which he is conscious 
he can make better time with far more ease than in the one he is 
forced to take. 

The trot appears from our analysis not to have been designed as the 
fastest gait, but for the medium one between the run and the walk, and 
when not urged too far beyond his supports; it is the strong business 
gait, in which he is capable of travelling farther in a day's journey with 
less fatigue than any other. It is owing to this fact that it has become 
the favorite pace in America, and has been cultivated to a greater ex- 
tent than in any other country ; indeed, we fail to learn anything of the 
trotting horse from any source before the importation of " Messenger," 
who was a thoroughbred running horse, and manifested extraordinary 
speed in the trotting pace after his arrival in America. It is very diffi- 
cult to discover wherein the mechanical proportions and points for a fine 
runner would not apply equally well to a fast trotter; and it is claimed 
that there has been no fast trotter who did not trace his pedigree to 
thoroughbred ancestry. This question, however, is beyond the pale 
of this essay, and has not been one that has particularly interested us. 
It will be difficult for one to believe that a new function has been devel- 
oped in the time that has elapsed since " Messenger's " importation, not 
yet a century, even by the most advanced Darwinian. It is much more 
reasonable to believe that, while great attention has been paid to breed- 
ing those qualities that insure speed, equally great care has been be- 
stowed upon training, so that the fast horse shall display his powers in 
the trot rather than in the run, of which he may be equally capable. 
In this way the fast trot becomes a habit with the individual, and in i 
he may excel his powers in the superior gait. But the habit is no 


heritcd, nor can it be transmitted to descendants, as is asserted by some 
authors. Functions and faculties, or the power by which acts are per- 
formed and habits acquired, may be inherited. No man is able to trans- 
mit to his off sprint; his acquirements, whether of mind or body. The 
child of the most profound scholar will not know one letter from another 
until he is taught them, and will learn them no more easily for all his 
parent's attainments. Nascilur, non Jit (horn, not made) is as true 
in this sense now as ever it was. The faculty through which the 
parent was enabled to acquire any accomplishment, whether mental or 
physical, may be transmitted to offspring. Even these are not congeni- 
tal or coincident with birth, as the function of breathing is; but the 
tendency is inherited, and the functions will be developed at the 
proper time, and in the order that their exercise will be required, first 
for the existence, protection, and development of the individual, then 
for the full employment of all the powers successively with which it 

mhnved by inheritance. The law of inherited or constitutional 
disease is the same ; all are not congenital, but most of them are 
developed, like consumption, at the age of puberty, and others, like 
cancer, at mature life, from inherited tendencies. 

When the colt is seen soon after birth, he must be helped upon his 

and the first efforts of his long and feeble limbs are to walk, in 
which he instinctively obeys the law to alternate the limbs and so pre- 

its balance. More than this he cannot do. Visit him a few days 
later, and he will be found not only able to walk with firmness, but to 
trot away from your approach. When you next visit him, after a 

r interval of time, he has acquired much greater control of his 
locomotive organs, and he will move off in a trot with no uncertain 
step, and, if you pursue, he will break into a run (Plate XLII.). 

The last pace is no less intuitive than the first, but required a 
longer period for its development. It is an acquired pace, but not 
the less intuitive. There is great doubt whether the complicated 
movement of the run, which has so long eluded the comprehension 
of man, was ever any better understood by the most sagacious of the 
quadrupeds that practised it ; and the identical character of the move- 
nent through so many species of them shows that it is inherited, or 


natural. The walk, trot, and run are all equally natural, and each is 
best adapted to each of the three degrees of speed which the animal 
finds it convenient or necessary to employ in his feral or unbroken 

It will be seen that the theory of the trot is the same as that in the 
run, namely, that the centre of gravity shall be supported constantly 
and propulsion made uniformly by all the extremities from the lime 
they reach the ground until they leave it, but by two alternate limbs 
at a time, and not by one as in the run. The action of the limbs in 
shortening and extending, to enable them to begin the support early 
and continue it late, and permit the centre of gravity to pass over them 
without being deflected, is the same in both paces. The action is 
the same, differing only in degree. The undulations are greatest in 
the slow trot, and diminish as the speed is increased. Every rider 
knows this from experience ; the uncomfortable trot is the slow one. 
The reason for this was explained when treating of the run in the last 
chapter. In the slow trot the action of the muscles is not sustained, 
and the bony levers are allowed to resume their normal angles. At 
each half-stride the centre of gravity regains nearly, if not quite, its 
elevation ; but as the horse increases his speed he lowers the centre of 
gravity, and, in so doing, enables the extremities to reach farther and 
sustain the weight longer, while the rapidity of the movement of the 
body gives it a momentum that forces the suspensory ligament to yield 
and the angles to close to the requisite degree to prevent the alternative 
of deflection of the trajectory, or crushing of the limb ; and if measure- 
ments be taken of the height of the horse at different portions of 
the stride, it will be found that it is least when it would seem that 
it should be the greatest, that is, when it passes the perpendicular, or 
that point where the supporting limbs are shortest, as was shown in 
the last chapter when analyzing the action in the run. 

While the action of the limbs in the two paces is similar, the co- 
ordination of them presents some interesting points for consideration. 
Instead of the great impulse being given by the fore leg, as in the 
run, it acts in a lesser degree, raising the centre of gravity only so far 
as to give its co-operating posterior extremity an opportunity to use its 

















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nil-: iioKsr. IN MOTION. 113 

propelling power in the direction of the centre of gravity, as in Un- 
bound of the deer and the leap of the horse ; for if it were given 
above it the animal would be pitched headlong. The hind foot should 
be the last to leave the ground on a priori reasoning ; and on consulting 
the silhouettes of the trotting horse (Plates XXXVI. -XL.), such will 
h found to be the fact. The early start of the fore foot enables it to 
clear the way for the hind one on the same side to advance to the 
support of the centre of gravity in its turn without being hit by it, or 
overreached, as it is technically called. In the mean time the fore 
foot, having a more circuitous route to travel, is enabled to attain its 
position as a supporter at the same instant as its co-operating 

The position in which the feet fall is as nearly on a line as is possi- 
ble without their interference, both in the trot and run, as may be 
seen by referring to the illustrations of the paces in the latter part 
of this volume, where the animals are seen in various aspects of the 
same position. 

Interference with the posterior feet is rendered very difficult by the 
mechanical arrangement of the hock joint, already explained, which 
causes an involuntary circumduction of the hind feet as they pass each 
other, and yet compels the feet to be planted successively near the 
same base line. In the case of the anterior extremities there is no 
corresponding contrivance, but the breadth of the shoulders renders it 

For obvious reasons it is not possible to show by the camera the 
occurrence of interference, but overreaching is shown in Plate XXXVI. 
Figs. 2, 10, and in Plate XXXIX. Fig. 9. The fore foot being dila- 
tory, or the disproportion in the length of the body to that of the legs, 
exposes the fetlock and heel to injury from the shoe of the hind foot ; 
but generally the hind foot is pushed under the forward one as the 
latter rises. 

There is a pace closely allied to the trot, and differing from it 
only in one particular, and that is that the limbs do not move diago- 
nally in pairs, but those on the same side move together. This pace is 
shown in Plate XLIX. Comparing this series with a trotting series 


(Plate XXXVII.), it will be found to be impossible to distinguish one 
pace from the other, as shown in the silhouette. This pace is called 
racking, or pacing, in America, and ambling in England. The objec- 
tion to the name pacing is that the word pace is used constantly as a 
general term for all the different modes of progression, and therefore 
leads to ambiguity. While in the trot the centre of gravity falls near 
the intersection of the two straight lines drawn through the diagonal 
footprints, in the amble it is shifted from side to side, as the right or 
left feet alternately support the weight. The effect of this is to give 
a rolling motion to the body like that of a ship with the wind abeam. 
It is an easy pace for the rider, being free from the sharp undulations 
of the trot. The necessity which exists of rapidly changing the base 
of support from side to side makes it practicable in the horse only 
when the speed is considerable, and quite impossible in the rate pur- 
sued in the walk. In the camelopard, owing to the shortness of his 
body and the great length of his legs, it is the only method of loco- 
motion possible, as he would overreach in the paces used by the horse. 
He is able to make progressive motion in this way at whatever rate, 
from the great elevation of the centre of gravity, and the consequent 
slow oscillation of it ; for the time of its oscillation increases with the 
length of the line from the centre of gravity to the base of support. 

The amble is natural to some horses, which take to it instead of the 
trot; as some people are sinistrous, though the greater number are 
dexterous instinctively, and others are ambidexterous. 

Some horses are amblers first, and afterwards learn to trot and travel 
equally well in both paces ; indeed, considering the small proportion of 
horses that fall into this pace,, and the record made by them on the 
turf, it may be thought to have no disadvantage over the regular trot. 
It would seem to give great advantage to a short-bodied horse, as there 
is no danger of overreaching. 

Many of the photographs reproduced in the photolithographs, and 
used in this volume to analyze the paces, were imperfect in lights and 
shades, and others, when the subjects were dark-colored, were in sil- 
houette, to which all were reduced. The outlines are quite perfect, and 
the details in other respects are quite unimportant to the study of the 






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movements. It is only necessary, in order to determine the movements 
of the several limbs, to suppose either of them to be right or left, and 
follow it as such throughout the stride. Examples have been selected 
of the two principal paces, when the horses were light-colored, to 
reproduce in heliotype, a process which furnishes an exact tran- 
script of the original photograph by the same agency, namely, 
the sun. 

The walk is the simplest of the paces, and best understood. It is 
defined to be that pace in which one foot is not raised until its fellow 
is upon the ground. The definition is as applicable to quadrupeds as 
to bipeds, if in the former we assume the two anterior and the two 
posterior extremities as pairs. The slow walk, or saunter, represents 
the pendulum of writers on animal mechanics, by whom the leg was 
supposed to swing like a pendulum on its centre, but little muscular 
force being used except to counteract the attraction of gravity. 

A man in walking throws the centre of gravity over the leg, which 
is to serve, for the moment, as a column of support, and leans forward 
until the centre of gravity is in advance of the foot as a base ; this ren- 
necessary the advance of the other foot to serve as a new base, 
and the action of the flexor muscles upon the toes, with the weight of 
the suspended leg, carries the centre of gravity diagonally forward until 
it is again supported by the other foot. These movements are all 
detailed and formulated by the old writers, and are referred to here for 
the purpose of bringing the science of animal dynamics, as it has 
been taught until now, freshly to the mind of the reader. 

It must be conceded that we have advanced the science of animal 
mechanics somewhat in this treatise, and demonstrated the fact that 
its problems are not to be solved by physics, as heretofore attempted, 
nor yet by vital force exclusively ; that animal motion in its highest 
manifestation is the resultant of both, chiefly of vital force, but neither 
can be ignored by one who would understand the subject. 

Each one of these elementary acts of progression is a step, and a 
series of them is a walk. The walk of a quadruped is more complex 
and perfect than that of a biped ; for while the latter is compelled to 
oscillate his body in order to balance it upon each foot alternately, the 


quadruped uses the diagonal feet alternately, so that the centre of 
gravity always falls within the quadrangle formed by them, and near 
the intersection of the lines connecting their diagonal feet. 

The theory of the walk in quadrupeds is that there should be 
two feet always upon the ground while the diagonal ones are being 
advanced, and if the legs moved synchronously in pairs, there must be 
four on the ground for a brief time at each step, for from the defi- 
nition of the walk one foot does not rise until the other is upon the 
ground; it follows that in two pairs of feet the two feet cannot rise 
until the other two are upon the ground. This, one would think, 
should be proved by the camera; but it shows that sometimes three 
feet are on the ground, but never four at the same time. How is 
this ? Is the definition of the walk incorrect ? It is so when applied 
to quadrupeds. In fact, the diagonal limbs do not act synchronously 
in the slow movements of the walk, for it is more difficult to maintain 
an equilibrium in a slow movement than a fast, as a top falls when 
its revolutions are slow, and for the reason that a horse never rests 
on two legs, but always on the two anterior and one posterior, so 
that the centre of gravity always falls within a triangle ; so in the 
walk one of the reserve feet holds the ground for a brief time until 
the other has the start, in order to shorten the time in which the 
centre of gravity has but two points of support. 

The walk, being the slowest pace of the horse, has been best 
observed and most discussed, but chiefly as to the order in which the 
feet are moved. There can be little doubt that habit in the horse, as 
in man, determines which foot shall be the first to move ; and it may 
often be determined by. their accidental relation to each other at the 
instant that he has occasion to move one of them, though it would 
be doing no injustice to the brute to suppose him to have a suffi- 
cient freedom of will to choose which foot he should put forward 
if he waited to think of it. 

When the horse quickens his walk, he does not at once change his 
pace, but extends his strides and makes them more uniform, until 
further extension becomes difficult, when he will break into a trot, in 
which there are never more than two feet upon the ground at a time, 


as has been already stated. This change from a walk to a trot is 
shown in the fine silhouette (Plate XLI.). 

Single-foot is an irregular pace, rather rare, and distinguished by 
the posterior extremities moving in the order of the fast walk and the 
anterior ones in that of a slow trot. These mixed paces are quite 
compatible, as they are of the same kind and move in the same diago- 
nal order. It is illustrated by Plate LV. The rhythm of the foot- 
falls is characteristic, and once heard will ever after be recognized, 
even in the dark. The same horse is made to illustrate the regular 
walk in Plate L. 



THE series of plates which follow are intended to show more fully 
than was possible in the silhouettes that precede them, the action of 
the horse in every possible position in all the paces ; they require, 
however, a brief explanation. 

The same ground was used as that on which all the experiments 
were made that are detailed in the Appendix ; but instead of a full 
battery of twenty-four cameras, only five were employed, and they were 
arranged in the manner shown in Plate I. (frontispiece). One only 
represented the battery, and that was in the middle of the series ; the 
other four were placed at nearly equal distances, two on each side, so 
as to represent the arc of a circle whose centre should be occupied 
by the horse at the moment he appeared opposite the central of the 
five cameras. At this point a thread was drawn across the track 
which, when the breast of the horse came in contact with it, made 
magnetic communication with all five of the cameras at the same 
instant, so that five views of the animal were produced at the same 
time, showing him from as many different directions. 

The time of exposure of the negatives was so immeasurably small 
that few of the pictures taken were perfect in all the details ; and as 
red appears as black in the photograph, so all bay horses were without 
any details of light and shade, simply as silhouettes ; and even when 
the horse was light or gray there would be some defect in some part 
of every one of the series. 

Experiments were made with various processes to reproduce them 
with all their defects; but it was found that the making of tlu 






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CP THE PAC E 3 . P/-.FI,' '.IN"O. 


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necessary transfers from the originals, while they reproduced accu- 
rately all the defects of the original photographs, reproduced them 
with diminished sharpness, and these methods were abandoned. 
Under the direction of the Heliotype Printing Company another 
plan was adopted. From the original photographs, by the helio- 
type process, copies were produced on gelatine magnified, and prints 
taken on Bristol board in blue ink in the same manner as 
in the ordinary heliotype process. These prints, with the originals, 
were put into the hands of artists skilled in drawing on wood for 
engravers, who drew them with a pen in india ink, under careful 
supervision of the writer, so as to preserve the outlines as they were 
rendered by the camera and avoid reproducing the blotted defects 
of the originals. These drawings were then reproduced on stone by 
the camera, reduced to their original size, and the prints given in the 
volume were printed from these stones as in ordinary lithography. 

They cannot fail to be of great advantage to artists, especially 
those who would perfect themselves in animal drawing, and that 
acknowledged difficult branch of their art, animals in motion. 

They and the public generally are greatly indebted to Mr. Stanford 
for the enlightened liberality with which he has pursued this costly 
investigation, and given its results to the public without any prospect 
of pecuniary advantage to himself. 

It will be observed that some of these pictures are so nearly alike 
that at a superficial view they appear the same ; but it is almost impos- 
sible that the times in which any two should be photographed should 
coincide, and there will be found no two exactly alike ; and the near 
approach to the same posture proves the universality of the law in 
which all the paces are performed. 

In some of these plates there are but four pictures; the fifth, owing 
to some serious defect or failure of the apparatus altogether, is 

Plate LVII. represents a position in the run corresponding with 

that in Fig. n, page 95, differing only in the fact that the right fore 

N performing its functions rather than the left, as in the cut. 

From this extremity the body will be projected from the ground, 



and the diagonal hind is advancing to the support of the centre of 
gravity. Comparing this with Plate LXV., in which one figure is 
wanting, the correspondence will be found so close that at first sight 
it is difficult to convince one's self that they are not identical pic- 
tures ; but on careful inspection it will be perceived that in the 
quartette the body is less advanced and the supporting leg is farther 
from the perpendicular. The missing picture should be the first 
in the regular order. 

Comparing again this plate with Plate CII., the body of the horse 
will be found to have advanced from the position in the former until 
the supporting leg is quite perpendicular, and the other limbs are 
relatively advanced. 

In Plate CIV. there is still further advance; the foot is under 
the centre of gravity, and the posterior extremities are being gath- 
ered under the body in the order with which they will successively 
take their turn. 

Plate LXXVIII. exhibits the same movement on the instant that 
the propulsive effort of the limb is concluded and the foot is leav- 
ing the ground. From this last position there is an interval of one 
fifth of a stride, in which there is no support given to the weight 
of the body, but it is moving as a projectile until the diagonal hind 
foot reaches the ground, which it is about to do in the following 
plate. The left hind foot will be the first to make the contact, from 
which we know that the right fore foot was the one by which the 
body had been projected into the air ; the right hind foot will follow 
and take the ground a step farther in advance. This plate may be 
compared with LXX., in which the right feet are in corresponding 
positions with the left, as seen in the former. Plate XC. represents 
the horse in a similar position. 

The slow trot is shown in Plate LIX., and is not distinguishable 
from the fast walk, as seen in the succeeding plate ; it is only when 
the instant of exposure of the sensitive plate of the camera is coin- 
cident with that in which all the feet are off the ground that the 
walk can be distinguished from the slow trot. 

Plate LXI. is also an attitude of the trot, but it is recognized by 


the higher action of the free limbs, and this action indicates a higher 
rate of speed than is possible in the walk. 

In the succeeding plate the walk is again represented and is un- 
;kable, as the three feet are supporting weight, as indicated 
both by their position and the yielding of the pasterns. 

In Plate LXIII. we see the sluggish run in which the speed or 
momentum of the horse does not permit the propulsion of the fore 
to carry the body clear of the ground before the hind ones come 
to the support of the centre of gravity prematurely, and which con- 
stitutes the pace known as the canter. (See page 103.) 

The fast trot is shown in Plate LXIV. Plate LXVI. seems to 
be a fast walk, in which the groom is urging the horse into a trot. 
The position may be interpreted into either a walk or a trot. 

Plate LXVI I. represents a position in the leap, and is fully ex- 
plained in the sixth chapter. 

The walk is further illustrated in the two following plates. 

In Plate LXXI. a position in the trot is shown where the feet 
arc all clear of the ground. Before the fore leg, which is extending 
forward to reach the ground, makes the contact, it must be straight- 
ened and the toes raised, as in Plate LXIV. As already stated, it 
is difficult in some of the "Illustrations" to determine a slow trot 
from a fast walk, for there may be an instant of time in the trot 
when three feet are on the ground. The mechanical action is the 
same in both paces, and the distinction is based on the speed. This 
difficulty could not occur where the reader has the advantage of a 
consecutive series of views, as is shown in Plate L. 

The heavy Clydesdale in Plate LXXI I. is shown in the am- 
bling pace in which the weight of the body is borne and the propul- 
sion performed by the two extremities of the same side. 

The canter is illustrated in Plate LXXVIII. The support is 
here given by the left fore leg, and the greater flexion of the diag- 
onal right indicates that it is the next in order to perform that func- 
tion. The degree of action indicates a low rate of speed, which 
could be attained in the trot with greater ease to the horse if not 
to his rider. 




Plate LXXXI. represents the animal in the greatest degree of 
extension he reaches in the run. The posterior extremities have suc- 
cessively performed their functions as supporters and propellers, the 
anterior limbs are extended to relieve them, and for the instant 
the diagonal feet are upon the ground, but it is only for an instant ; 
the weight of the body is already on the fore leg, and the only pro- 
pulsive force left in the hind one is derived from the reaction of the 
suspensory ligament and its reinforcing tendons. This position 
nearly corresponds with that in Fig. 8, page 93, though a little in 
advance of it. 

Plate LXXXV. illustrates the run in the position shown in Fig. 
10, page 95. The fore leg must be straight from the elbow to the 
foot when it makes contact with the ground, as only in that rela- 
tion of the bones forming the columns of support could the weight 
suddenly thrown upon them be borne. A moment's consideration of 
the mechanical construction of the knee-joint will suffice to convince 
one of this, and a weakness at that point which renders the animal 
liable to stumble is a very serious defect, and where it exists it in- 
dicates the loss of the balance of power between the flexors and 
extensors of the foot. This inflexible position of the knee-joint will 
be found to be universal in all the paces when the limb is sustain- 
ing weight. 







Tin: following account of the methods by which the original 
holographs were produced that served as the basis of the analysis of 
the paces, the results of which arc contained in this volume, was 
furnished by Mr. E. J. Muybridge, the photographer by whom they 
were executed. 

Some time in 1872 Mr. Stanford, being desirous of settling some 
controverted questions as to the action of the trotting horse, conceived 
the idea that the camera might be made available for that purpose. 
To this end he consulted with Mr. Muybridge, and induced him to 
undertake some experiments in instantaneous photography.* The 
experiments made at that time were inconclusive, and for several 
years. Mr. Muybridge being absent from the State, the matter rested, 
though it was not abandoned by Mr. Stanford. 

In 1877, Mr. Muybridge having returned, the experiments were 
renewed. A few pictures were taken of " Occident " while in motion 
a noted trotter, owned by Mr. Stanford with a single camera; 
and one of these, representing him with all his feet clear of the 
ground, was enlarged, retouched, and distributed among various 
parties interested. 

Instantaneous pictures were defined to be, at that time, in ordinary photographic par- 
lance, when the exposure has been very brief, or under half a second. In the liritish Journal 
Photographic Almanack for 1868 it is stated that good street views had been taken in a twelfth 
part of a second. The conditions, as there given, for extreme rapidity of exposure are a good 
and quick-acting shutter, a lens with a large angular aperture, and chemicals in perfect 



The result of this experiment was so successful that Mr. Stanford 
determined to try another one on a more extended scale. He 
assumed, if one picture could be taken instantaneously, why not an 
indefinite number, and by increasing the number of cameras increase 
to the same extent the number of views, and illustrate the various 
positions in an entire stride ? 

Mr. Muybridge was authorized to procure the needed apparatus, 
and a building suitable to the purpose was erected on the west side of 
Mr. Stanford's private track at Palo Alto (see frontispiece). In the 
following year, 1878, the preparations were complete; every resource 
of the photographic art had been provided that was thought to be 
required or attainable. Twelve cameras were placed in the building 
at intervals of twenty-one inches, with double shutters to each. These 
shutters were arranged, one above and the other below the opening 
through which light was admitted to the lens, and held by india-rubber 
springs, constructed in the form of a ring, with a lifting power of one 
hundred pounds, and secured by latches, to be liberated on the com- 
pletion of a magnetic current.* 

For the purpose of making the exposures at the proper intervals 
of time, a machine was constructed on the principle of a Swiss music- 
box, having a cylinder with a row of twelve pins arranged spirally. 
This was put in motion by a spring, and, as it revolved, each pin in 
succession established a magnetic circuit, with the magnet connected 
with each of the twelve cameras in succession, and the whole series of 
exposures was made in the time occupied by a single complete stride 
of the horse. 

* This description of the shutters and their mode of action is somewhat obscure. The 
shutter, as described by Kleffel (Handbuch der Practischen Photographic, Leipzig, 1874, p. 201), 
is as nearly as possible the double shutter used by Muybridge. Kleffel's shutter was held by 
a spring, and when the picture was to be taken the spring was touched, and the shutter, which 
had an opening through its centre, dropped past the lens, exposing the lens to the light during 
the time of the passage of the opening across it. He recommended weights to be used when 
greater rapidity was required. Muybridge's modification of this consisted in the use of rubber 
springs in lieu of weights as recommended by Kleffel ; though no claim is set up by him to 
priority in the use of rubber springs, as one Thomas Skaife obtained a patent in England for 
rubber springs for camera shutters as early as 1856. 












This arrangement gave the attitude of the horse as he arrived 
before each of the cameras in succession at the instant of exposure of 
the negatives. In practice it was found to be extremely difficult to 

the apparatus in motion at the exact time required, and to regulate 
it to correspond to the speed of the horse. 

This contrivance was found to be best adapted to the more irreg- 
ular movements of other animals, as the running of dogs, the flight of 
birds, feats of acrobats, etc. It was desirable to find some method 
that would better represent the regular movements of the horse, and 
which should be regulated by his own movements. 

On the side of the track opposite the building where the cameras 
were placed, and in such position as to receive the best exposure to 
light, a wooden frame was erected, about fifty feet long and fifteen 
high, at a suitable angle, and covered with white cotton sheeting 
(Plate CVII.), divided by vertical lines into spaces of twenty-one inches, 
each space being consecutively numbered. Eighteen inches in front 
of this background was placed a base-board twelve inches high, and 
on which were drawn longitudinal lines four inches apart. In front 
of this base-board a strip of wood was fastened to the ground, upon 
the top of which wires were secured at an elevation of about an inch 
above the ground and extending across the track. The wire was 
exposed in a groove to one only of the wheels of the sulky, being 
protected from contact with the horse's feet and the other wheel. 
Each wire was held in proper tension by a spring on the back of the 
base-board, so arranged that when the wire crossing the track was 
depressed by the wheel it should draw upon the spring connected 
with it, and make contact with a metallic button and complete the 
electric circuit. 

These wires were placed at distances from each other correspond- 
ing with the cameras on the opposite side of the track, and with the 
spaces between the lines drawn on the background. 

From this description it will be readily seen that the depression of 
the first wire would complete the circuit and cause the magnet con- 
nected with the corresponding camera to move the latch and liberate 
the shutters, exposing the sensitive plate for a space of time that is 


hardly conceivable. In like manner, as the wheel passed over the 
second wire, the shutters would be liberated on the second camera, and 
so on until the whole series were discharged. When the horse passed 
with great velocity over the wires these shutters were discharged with 
such force and rapidity that the horse was not unfrequently startled 
and broke his gait. 

If everything was properly arranged the driver had but to keep the 
wheel of his sulky in the groove which was sunken for it, and it 
would, by depressing the wires successively, take the pictures at every 
twenty-one inches until the whole series were taken. 

The method just described was used in all cases where horses were 
driven to sulkies ; but when wheels were not used this arrangement 
with wires under the track had to be modified, and a thread was 
drawn across sufficiently high to come in contact with the horse's 
breast, and strong enough to cause the contact and establish the 
circuit as before, but not so strong as to wound the horse when 
going at full speed. 

By these methods many views were taken and distributed to all 
parts of the country : they attracted a great deal of attention, and 
elicited a great variety of opinions and not a little ridicule ; some 
artistic persons displayed great ingenuity in burlesque, no one under- 
stood them. 

The number of cameras was afterwards doubled, and they were 
placed at intervals of twelve inches to still closer analyze the move- 
ments of the horse. Lines were drawn across the track at correspond- 
ing distances, and the numbers indicating them, instead of being at 
the base of the screen, were on a board between the horse and the 
cameras. The heliotype plates Nos. CVI. and CVII. represent the 
battery of cameras and the screen as they were when twenty-four 
cameras were in position. 

The whole of the series of twenty-four figures each used in this 
volume to illustrate the paces were taken in this manner. They were 
very accurately taken, and are specimens of the best results attained 
after years of expensive experience ; and the heliotypes are perfect 
transcripts of the original photographs. 


It will readily be understood that the accuracy of these analyses 
upon the uniform tension and strength of the threads con- 
nected with the springs through which the circuit is formed. The 
perfection of the pictures depends upon the sensitiveness of the chem- 
icals and the time occupied in their exposure to light. This time is 
as nearly instantaneous as can well be conceived. Mr. Muybridge 
estimates it by comparing the enlargement of the horizontal diameter 
of an object photographed with the vertical diameter of the same 
object at one five-thousandth of a second. This can only be deter- 
mined by measurement, and that approximately even in objects of 
considerable size ; it is so nearly instantaneous that there is no 
appreciable loss of proportions from differences between vertical and 
horizontal diameters. 

University Press: John Wilson & Son, Cambridge. 




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